Thursday, November 16, 2017

Bench pressing

As alluded to in last week's post about Guardiola's "wild" rotation (or lack thereof), I am currently of the opinion that the various City options that are available (plus a couple of other elite players around the league) are so good that it is worth absorbing the inevitable rotation hits that come, even as those punches start to increase in number over the busy holiday period. One of the risks and possible downsides here is that with rotation generally not being something one can plan around (unlike, say, actual injuries or suspensions), the characteristics of your bench need to be tweaked somewhat.

Two key points need to be changed in my own personal bench strategy. First, I need to pay more attention to it. I am generally pretty focused on maintaining a good substitute keeper that rotates nicely with the other option and then one other sub, but after that I do not prioritise having a deep bench. Second, because you won't necessarily be able to choose when to deploy your bench options, I think you are better focusing on higher frequency scoring events such as clean sheets or bonus points rather than just goals. For example, if 2 players are each expected to play 90 minutes in each of the next six games with one projected for 3 - 3 - 5 - 2 - 3 - 3 points where as the other is projected for 2 - 3 - 4 - 7 - 2 - 2 then while the second player is expected to score an extra point overall, one can make the argument that seeing as you expect to deploy this player just once or twice, you are better off with the 5/6 chance of earning more than 2 points with player one than the 3/6 chance with player two. Of course, this only applies to an extent and if there is a bargain player who offers significant scoring potential then they are obviously the better pick.

The below table shows midfielders and forwards available for under 5.0m (though you can set the threshold as you wish) and plots the percentile they fall into with regards to:

  • the share of their team's BPS they account for (which I am using a proxy for bonus point potential),
  • clean sheets (for midfielders only)
  • expected goals
  • expected assists

I have highlighted a few names below the chart that I will personally be considering as stocking stuffers for the holiday season.



Tom Carroll
Carroll has a bit of a cult following in fantasy circles though despite his promising underlying numbers he hasn't really been able to produce much by way of concrete returns. Here though we're interested not just in his assist potential but also Swansea's reasonable clean sheet record and his solid share of BPS which suggest bonus points could flow his way, especially given Swansea's lack of established stars. However, the model doesn't really like Swansea's defense going forward and their opponents in January - TOT, @NEW, LIV, ARS - make me nervous. Still, he's played every game and doesn't look likely to lose his place to the ineffective Sanches and so for 4.5m Carroll remains a reasonable bench option.

Nemanja Matic
Matic was one of the players I had in mind when considering this strategy and the data supports this thought process to a degree. What you're buying here is a very high chance of a clean sheet to accompany an almost guaranteed appearance, though bonus points are always going to be hard to come by with several other good players in this United side. I would prefer Matic at 4.5m as you are really not getting a great deal of offensive threat here but the fixtures from mid-December to mid-January are so good that one could easily see him racking up five clean sheets in eight games, which is just as good as a goal but spread evenly over the fixture list.

N'Golo Kante
Kante was the other player I had in mind when I started this and he too looks like a decent fit here. Chelsea's defense isn't quite as good as United's to date, although the model likes them slightly more in the coming weeks. Kante also provides a fairly significant increase in attacking potential, though again doesn't offer much by way of bonus point potential with other players like Morata and Azpilicueta attracting the lion's share to date. Given his increased attacking threat and Chelsea's incredibly favourable run of fixtures in December and January, Kante is my number one pick here, even at a slight premium to some of the other bargain basement picks.

Tom Cleverley
Richarlison has rightly won the plaudits in this Watford midfield and Doucoure has received serious backing having notched 4 goals to date already, but I actually quite like the unheralded Cleverley as a bench option here. The former United man actually has a slightly higher xG than Doucoure (though neither offers much to get overly excited about with Doucoure's 4 goals from 5 SoT incredibly unsustainable) though it's once again his ability to chip in across the categories we're interested in. Watford's defense projects reasonable well despite being leaky of late and another healthy of fixtures over the holidays look promising.
I'm still not entirely convinced by this strategy, with the other alternative being to grab 13 or 14 affordable players to build a balanced squad where your bench options can offer more than just scraps. With Aguero's potential injury I was considering this alternative strategy but I can't see not owning the Argentine, Kane and Salah when healthy which pretty much rules out a totally balanced side. Thus I will try and spend the next couple of weeks strengthening my awful bench for the inevitable rash of rotation frustration coming our way.

Tuesday, November 7, 2017

On Guardiola's rotation

There seems to be a growing chorus that Man City players are becoming harder and harder to own due to constant rotation from Pep Guardiola. There are two key pieces of information that are useful to assess how damaging rotation can be to a player:
  • The predictability of when the rotation happens (before of after Champions League games, away from home etc),
  • If not selected for the first team, how often do they come on as a sub. If you have a decent bench then - while frustrating - you can deal with players not playing at all. However, if they consistently come off the bench for only 15 minutes or so then you are lowering your odds at success.

Predicting team sheets is not really my forte (nor a particular interest) so we're going to focus on the second point here:


We can see four of the City options have spent time on the bench this season while De Bruyne and Silva have been ever present to date. The calculation for this pair is slightly different as you're getting increased certainty but with lower upside (their 5.8 and 5.5 points per appearance trail their teammates). De Bruyne also comes at a fairly significant premium which personally excludes him from consideration for my own team which I am looking to spread the wealth more evenly, but I can see the appeal of the Belgium's overall package.

Let's look at the other two midfielders first: Sane and Sterling. Each has spent some time on the bench, though Sane is coming off 6 straight starts and has clearly won the confidence of Guardiola despite his young age. The first point to note is how incredible this pair have been to date. For simplicity's sake I am going to continue to use points per game (PPG) numbers here (where as I would usually prefer underlying stats) but I do so with the confidence that their success has been anything but a fluke.

In his 7 starts, Sane has averaged 8.1 PPG, while Sterling slightly eclipses him with 8.2 PPG in his 6 starts. For comparison, the 25% owned Eriksen is averaging 5.7 PPG while his 21% owned teammate Alli is further behind with just 4.9 PPG. Thus, while it is extremely frustrating to have your player on the bench, you need to keep in mind that when they play, they are really operating on another level of production so far this season.

On the subject of being benched, between them, this duo have been benched 7 times, getting some playing time on all but one occasion. With the busy holiday period on the horizon I think these rest numbers could increase somewhat and there might be occasions where these players are completely left out of the days action, but, when they have been on the field for a short cameo, the results have been far from a disaster. In their 7 sub appearances, Sterling and Sane have averaged just 24 minutes but a frankly absurd 4.1 PPG. This number is of course skewed by Sane's brace against Liverpool but still, the pair have delivered returns in 3 of their 7 sub appearances. For reference, that 4.1 PPG compares favorably to how players like Firmino (4.3) or Ozil (3.3) have been performing while playing full matches.

Let's put together a scenario to see how this could play out, using Sterling as an example (who my model likes marginally more but you could replace with Sane without changing the conclusion):

In 10 games over the holidays, Sterling will get 7 starts, 2 sub appearances and will be dropped totally for one game. If he continues to average 7 PPG in those starts and 3 points coming off the bench then he'd accumulate 55 points. We'll then throw in another 2 points for your bench player who will replace him when he misses out. So a total of 57 points for an investment of 13.2m (8.2m for Sterling (or less if you've held him for a while) plus a 5.0m scrub on the bench who just needs to show up).

How else can we piece together such a return? Assuming we could find a player who will start every game over the holidays (doubtful) we're still struggling. Mahrez? 5.1 PPG. Mikhitaryan? 4.7 PPG. The pricier Alli? 4.9 PPG. Eriksen's 5.7 PPG would get you to the 57 points but you've spent 1.5m more money and need him to play every week just to break even. If you played the fixtures well, you might be able to do something with Richarlison and another mid-level option, but then, you can easily afford those players alongside Sterling anyway and it isn't like there is five of them to build a balanced, mid-range midfield (in fact, the list gets extremely limited after Richarlison, maybe Ramsey, I suppose GroƟ).

Let's build this the other way. Let's assume one of the above options can get you 50 points. At 7 points a start and 3 points per sub appearance, Sterling would need just 5 starts and 4 sub appearances to match that output. Then you've got to factor in the huge upside of him playing more due to injuries to others, being more productive off the bench etc, getting extended sub-minutes after City wrap up the game in the first 45 minutes etc.

Up front, one could conclude that the presence of Lukaku, Morata and Kane makes Aguero easier to ignore as they are ready made options who provide a great balance of upside and certainty. But, if you believe in his numbers to data, Aguero is operating on another level, averaging over 9 PPG compared to the ~6 PPG offered by his peers. This means that if Lukaku has continued his 5.8 PPG rate over the full 10 games, 5 games of Aguero plus 5 games of a bench scrub would also come to the same total (5x9 + 5x2 = 55 points). Throw in the fact that most people feel you need two of these elite forwards, and you now need to find two of these options who can match Aguero's prowess if you are going to ignore him.

Jesus is arguably the easiest player of the bunch to ignore given his more modest PPG total (6 in starts, 5.4 overall) and his relative lack of stature in the team.I It's true that City lack great depth up top, but Guardiola has also only deployed both his front men in 4 of 11 fixtures this season, and not since GW5 and one has to feel that Aguero gets slightly more games than his young teammate, all else being equal (Sterling or Sane could even be deployed up top if needed). If you are looking to really spread your money across the team though, I can still see a scenario in which the Brazilian makes sense.

Risks to this analysis
There are, of course, risks to this analysis. The most obvious is probably that City slow down and the gap their players enjoy over their peers is cut. This is definitely possible but I haven't seen many flags in their data to suggest it's on the horizon. You're also not locking anything in either, so if that does happen you are still well placed to jump ship for the other options discussed above. The next risk is that by using such a crude measure (PPG) we are being too simplistic and not accounting for quality of opponent.

However, over a 10 game run you are going to get a reasonable averaging out of opponents and in this particular case, City's 10 game stretch from Dec 3 - Jan 20 is arguably no harder than their fixtures to date, with only three fixtures looking really tough on paper (@MUN, TOT and @LIV although the latter might even be a stretch given the way City massacred Klopp's men in GW4).

My own approach
Personally I am happy to absorb the risk associated by Aguero, Sterling or Sane but will place extra emphasis on sorting out my bench to ride the inevitable benchings. This City side is special and with several mid-priced options available to get access to it, I simply think the opportunity is too good to pass up.

One small side note, is that when selecting my bench I am going to lean more towards certainty of playing time and look to players who might log consistent extra points from clean sheets or bonus points, knowing that they will be called into action but without me being able to choose when to deploy them. This means that players like Kante and Matic will come into play, more so than the likes of Choupo-Moting or Ince who project well but lack the consistent returns to justify the higher price tag given their specific role in my team.

Wednesday, November 1, 2017

Expected Goals - a comparison with Opta

The popularity of "expected goals" as a metric has exploded over the past year or so, with mainstream TV broadcasts now starting to dip their toes in the water of advanced analytics. One inevitable, if slightly unfortunate, consequence is that there are now multiple xG models, which could potentially disagree by a reasonable amount, which to those who need a bit more persuasion as to the merits of statistical analysis, might suggest a lack of accuracy. This has somewhat been the case in baseball with the two big "Wins Above Replacement" (WAR) metrics sometimes disagreeing by a relatively large amount, especially when it comes to valuing pitchers. There is sound methodology behind each metric, of course, but for those who aren't well versed in the intricacies of the debate, the differences can be distracting and serve as fuel for those who want to dismiss analytics and focus on old fashioned "eyeball tests" etc.

I, of course, have my own model which probably predates a lot that are currently around but also lacks some of complexity that is now possible with the proliferation of individual event-by-event data from Opta, which allows one to do a better job at understanding the likelihood of a goal based on the exact location of a shot. My concern is that this model is confusing issues, although with my readership of 15 people against the millions of people exposed to Opta stats, this isn't a huge concern!

Nevertheless, let's first take a look at how different my model is than Opta's, then have a look at a few examples of the kind of player my model gets wrong, and then finally a few words on why you should continue (or start!) to care about the projected data in these electronic pages.

The above data is only based on 2017-18 data and the correlation looks very promising (an 88% r-squared is likely distorted a bit by a high volume of players with very low xG, but still, you can see a strong correlation between the two models and not many wild outliers), especially as there is still something of a small sample size issue with just 10 games in the bag. In terms of looking historically to analyse a game that has happened there is no argument that the Opta model is more sophisticated than mine but I am happy that the data here shows that what I've been offering is at least based in science and comparable to those more learned than I (thanks to ill advised transfers and a failure to heed my own advice, the league position of my own fantasy team doesn't always give the same assurances).

We can however see a few names whose xG varies quite significantly between the models and I want to highlight a couple of these to illustrate where my numbers need to be taken a pinch of salt:

Harry Kane vs Romelu Lukaku
Readers will know that my model loves Kane and he's been the top ranked player for much of the season. However the Opta model liks Lukaku a little more to date with the United man being worth almost a half goal more than his Spurs rival. In terms of sheer volume of shots, this outcome is hard to compute, with Kane taking 20 more shots than Lukaku and outshooting him 38 to 31 inside the box (all in one game fewer after this week's hamstring issue). If you want to take one step further away from shots then Kane still enjoys an advantage with 67 touches in the box to Lukaku's 54. Opta's model therefore must see some additional value in the quality of those chances, which is somewhat hinted at in his 12 big chances compared to Kane's 10. United have been more clinical, converting 18/29 (62%) of their big chances and 21/94 (22%) of their SiB compared to marks of 11/20 (55%) and 16/98 (16%) respectively for Spurs, though this argument gets a bit circular as others would argue that this efficiency is an effect of Lukaku's presence rather than Lukaku's conversion rate being a product of the team.

In short, the difference here isn't huge but is noteworthy and I will try and tweak my model a bit to increase the weighting given to team conversion rates (this data is factored in, but especially at this early stage of the season I heavily regress it back to league averages).

Man City
I feel like everything I write this season includes a section on Harry Kane and Man City and so here we go again. We can see that the Opta model rates Sane and Jesus's seasons significantly higher than mine, though interestingly Sterling and particularly Aguero are much closer (with the Argentine being almost 1:1). Like Lukaku above, this is almost certainly a recognition of the quality of City's chances, although watching the games I would have thought Sterling would really benefit from this as he seems to have gotten multiple tap ins this year with his pace enabling him to catch up with counter attacks and arrive at the far post for a square ball and easy goal. Still, this one makes total sense and will again be helped by an increased weighting in team conversion rates. Although, I don't think folks really need a model to tell them that this team is red hot, and the decision is really between Sane, Silva and Sterling or Aguero and Jesus, and adjusting the team rate wouldn't help you there.

Dominic Calvert-Lewin, Eric Maxim Choupo-Moting and Andy Carroll
This unlikely group of players is a cautionary tale of over-valuing solid stats from players on poor teams and could possibly be awarded the Adel Taarabt Memorial Trophy. I will focus on Calvert-Lewin because I own him and have thus paid most attention to his games (enduring 90 minutes of Everton with regularity is true dedication). The leaderboard among forwards in SiB goes Kane, Lukaku, Aguero, Morata, Lacazette, Calvert-Lewin, Jesus. One of those things is not like the others. That group ranks 1st, 2nd, 3rd, 4th, 6th and 10th among forwards in fantasy points and Lazazette has the worst goal haul with five. Calvert-Lewin is 25th among forwards with a measly 25 points and zero goals. Here I think the issue is both a team problem (Everton have converted just 6/66 (9%) SiB) and Calvert-Lewin himself, who just doesn't seem to be taking quality shots and, watching the games, he is lively but really doesn't seem like someone with crippling bad luck. He's hit the target six times, which in a vacuum would suggest more like 1-2 goals rather than zero, and there remains solid reasons for not overly focusing on SoT over SiB due to small sample size noise, but still, I think there's probably a gap in the model and also in my common sense in overly relying on it when it comes to players racking up shot totals without digging a little deeper as to their quality. This one is harder to fix without the advanced data so it might just be a case of raising those flags before highlighting this kind of player for potential success.

Looking forward
The pleasing thing about this bit of analysis is that while we can definitely identify blind-spots in my model, it's close enough to the Opta version to suggest we're on the right path. The reason this is exciting is because by basing the xG on simple events like shots and SiB, I feel we have a good chance at predicting future xG, which becomes trickier if you are trying to forecast not only how many shots Harry Kane will get, but where he will take them from, where the defenders will be, who passed to him etc. I hope that team shot data stabilises relatively quickly and is less impacted by individual idiosyncratic events and thus we can use it with some certainty to predict team totals which can be allocated to each player to give us our predicted shots to form the basis of xG.

I am not of course suggesting in any way that my model is as good as some of the others out there at determining why what happened, happened, but in terms of translating that data into predictive information I think we're in a good place and I'm fairly happy with how the model is working for now.

Gameweek 11 Projections

Thursday, October 19, 2017

Gameweek 9: Expected Points (or, a tale of one City)


I don't recall there ever being a side in the Premier League with so many viable fantasy options. The 2009-10 Chelsea side that scored 102 goals had Drogba, Lampard, Anelka and Malouda all with double digit goals but there's a non-zero chance that this City side could have four players approaching those totals by the holidays plus two of the best two creative players in the league in Silva and De Bruyne.

This week they have the top five xP players - which is simply absurd - and even Sane could be argued to be higher as he's currently still being penalised for his early season sub appearances (though with Aguero back I'd personally argue they remain a risk). The real heartbreaker is that this game against Burnley looks delicious and someone is going to be benched and disappoint a lot of managers. Everyone except Aguero played midweek against Napoli so there are no clues there, but this is in theory the third game in which Aguero was fit enough play after his broken rib so you have to feel he's in with a good chance of displacing someone. It also wouldn't be a huge surprise to see Gundogan get some minutes here or there. Of course, there's nothing that can be done other than make sure you have a deep enough bench to absorb the blow and brace yourself for disappointment somewhere around 2:30pm on Saturday.

Kane's ranking shows that to a degree he is a fixture proof, though the model is certainly tempering expectations compared to his prior month of action. Reports of his demise are absurdly premature though.

The big surprise here is Lukaku, who I was personally considering for my captain given the risk noted above for my City players. The model believes in this Huddersfield side's defense, whose 5 goals conceded at home put them solidly in the middle of the pack, with their +/- numbers being even stronger after their home record was blown up by Spurs in GW7. United meanwhile have been somewhat pedestrian away from home with +/- numbers of -43% (Liverpool), -21% (Southampton) and 5% (Stoke) following their impressive display at Swansea in GW2 (60%). With goals in three of those fixtures Lukaku has shown he can score without needing too many chances but his points hauls of 6 ,6, 7 and 2 away from Old Trafford do show that he probably lacks the consistent upside of an Aguero or Kane.

Points vs Expected Points: Gameweek 8



Given the short gameweek, I only have one main topic this week: Man City (and then a couple of words on Harry Kane).

Whether you just saw the goals, highlights or whole game, there was no denying how impressive City's demolishing of Stoke was this week. All six of their starting midfielders and forwards amassed at least 31 points under the official BPS system, compared to just two players total from United, Chelsea, Spurs, Liverpool and Arsneal (Bakayoko and Eriksen). Jesus was given the most points under that system (which overvalues goals in my opinion), De Bruyne was awarded Man of the Match at the stadium while Sterling earned the most fantasy points thanks to his goal, two assists and bonus points. In short, there's a lot of talent to go around here. Two things jumped out this week about this City side that need a bit of exploring:

1. It's increasingly difficult to select just three City players given the talent on offer. Silva, Sterling and Mane are all performing incredibly well, especially given their reasonable price tags, while Aguero and Jesus are first and fourth among all forwards in points despite missing time through rotation and injury respectively. Finally, the defense projects as the best in the league in many metrics, making Otamendi and Stones very attractive options for under 6.0m.

While the defense has been good - with 5 clean sheets already - this week's couple of sloppy moments against Stoke remind us how fragile clean sheets can be and with City in free scoring mode, I wonder just how committed they will be to keeping opponents out when they're three and four goals up every week. If they had a player who looked to be heavily involved on at attacking front too I would probably stick with him, but Otamendi projects as the best attacking threat with a good-but-not-great profile and so I can't help but conclude that the best way forward is with a couple of midfielders and one of the forwards from this dynamic side.

2. Which of those players I would select brings me to the second point. Without seeing the game one might think City were a touch fortunate, given that they scored 7 goals on 12 SiB and 11 SoT. Both those totals are of course great - and led the league this week - but they'd generally be more suggestive of a 3 or 4 goal haul rather than a 7 goal demolition. Now in part the team probably was a touch "lucky" - Fernandino likely won't hit another shot like that for a while and Bernardo Silva's effort took a bit of fortune to setup - but on the other hand, they really did feel like they would score every time they went forward. Between them, the six goalscorers registered 8 shots on target and scored 7 times. Some regression is coming but we also need to concede that a chance created by that De Bruyne pass is not the same as a Oxlade-Chamberlain cross wildly thrashed into the box.

Other expected goal measures account for this for past events (based on positions shot were taken from) but I don't know if we have a good grasp on how to project this going forward other than to mentally note that xG totals for the likes of Aguero and Jesus may well be suppressed in the model due a lack of recognition of the quality of player they are working with. Without having the more detailed Opta data my options are a bit limited but my idea is to work in the G vs xG vs shot data thar's available into my team conversion rates to try and capture this nuance.

**Side note: thanks to follower @fisksektionen for reminding me to figure out why Sane was absent from the upper tier of the model forecast. It turns out I had missed an accent over the e-acute which messed up the lookup formula. He's now right up there, alongside teammate De Bruyne**

Harry Kane
7 expected points on a league best 6 shots (3 SiB): he'll be just fine. 86,000 managers aren't as convinced and have sold Kane this week, though that move if defensible if it's a short term play to flip over to Aguero, Jesus or even Morata while Kane endures three tough opponents in the next four games. Indeed, in two of the corresponding fixtures last season - Liverpool (H) and United (A) - Kane didn't notch a single SiB. It's fair to say he's elevated his game somewhat since then though so I wouldn't be too despondent about holding onto the England frontman, especially with that oh-so-juicy sweetener against Palace sandwiched in the middle of those tougher fixures and then a run of games that takes you well past the holidays with only one - Man City (A) really scary game.

Thursday, October 12, 2017

Gameweek 8 Projections (or, why can I only have three Spurs players?)



Captain Notes
Despite not boasting an overly impressive set of results to date, the model rates Liverpool's defense quite highly and thus perennial captain option Lukaku is well down this week's rankings. Morata is a injury risk which is unfortunate given Chelsea's visit to lowly Palace, although even if fully fit the model is not enamored with the Spaniard thanks to so-so shot data for Chelsea on their travels. While they've racked up a very impressive 8 goals in 3 games, they've done so on just 21 SiB and 12 SoT, which makes the model cautious of future regression. For context, Arsenal have 20 SiB and 8 SoT in their three away trips and have yet to score.

With Aguero out and City at home, Jesus is a very real option and I might have him second on my own adjusted list. He gets a good share of City's chances when on the pitch (24%) and while his SiB numbers cannot match the likes of Kane or Lukaku, his Big Chances per 90 minutes are right up there and he looks well placed to get on the scoresheet again. Of course, going by the model that is all moot, as if you own Kane you will surely captain him. The only question is whether or not to give him the triple captaincy. The model ranks this as tied for his second best fixture in the next 12, with the top option strangely coming on the road thanks to Watford's stupendously awful defensive start to the season (41 SiB surrendered in three games with a SiB- +/- of 61%). Gun to my head I'd play the odds with the GW11 fixture at home to Palace but the certainty of knowing Kane is fit right now, and not coming off a massive fixture against Real - as he will be in GW11 - is not to be ignored.

The left field (well, left back, (sorry)) option based on the model is Ben Davies - who is now widely owned but not necessarily considered in the same light as his more esteemed colleagues. However, the model gives Davies a ~40% chance at a clean sheet, a 60% chance at an assist and a 20% chance of a goal so one might argue that the chance of him drawing a 2-point blank is arguably lower than Kane (who has done so four times this season). Again though, it's very hard to ignore Kane.

Quick rental option
If your team is in good shape then you might have the privilege of bringing in a player for just one or two gameweeks. For example, I knew I wanted Sterling in the medium term in place of the ineffectual Mahrez but with City travelling to Chelsea and United facing Palace at home I brought in Martial as a one week loan (with so-so results as Martial was limited to bench duty but did manage to nab a sneaky assist).

This week there is likely to be plenty of movement among elite forwards with injuries to Morata and Aguero, and uncertainty around Lukaku's status (not to mention a tricky trip to Anfield). As noted above, Jesus is the obvious pick and I see him as more than a one or two week play but many managers - including your lowly blogger - are already maxed out on City options so would need to look elsewhere.

I know Vardy has received buzz in this category but he has his own injury issues and so I'm going to go with Lacazette as a player I might target for 1 - 3 gameweeks while I wait for the dust to settle after the turmoil among the other elite forwards. His numbers don't generally blow me away but Watford has been miserable at home and with Ozil and Sanchez potentially both in the side, the chances should be plentiful for the Frenchman.

Monday, October 9, 2017

Points vs Expected Points: Gameweek 7


With 8 clean sheets and big performances from the likes of Spurs, United and to a degree Arsenal, there were points a plenty this week, though as we can see above, not all those performances were necessarily backed up by the underlying stats. A couple of names to focus on here:

Alexis Sanchez
The model liked the Arsenal man as the best performer of the week with 10 expected points on 8 shots (4 SiB) and 6 CC. The "three elite forward" strategy which was en vogue for all of 2 weeks has been devastated by injuries to Aguero, Morata and Lukaku and so managers are now looking back to elite midfielders to lead their team and Sanchez is well placed to potentially fill that role. His incredibly low ownership number of just 3%, plus his earlier price fall make him an incredible opportunity to turn a profit if (or should we say when) his actual points haul starts matching his xP. Arsenal's fixtures are good but not spectacular as they face City and Spurs in GW10 and 11 and the model doesn't think they're in the same league as City or their North London rival, but you have to also factor in that Sanchez will likely represent a huge share of Arsenal's SiB and CC and is about as locked into the team as one can be when healthy (the lack of Champions League involvement could be a rule boost there too).

Fantasy squads are built as a whole, so looking at one or two individual spots in isolation isn't always useful, but if you'll permit a thought experiment, consider this. You need to fill two spots: a forward and a midfielder, and you currently have Lukaku at 11.6m and Silva at 8.4m (i.e. 20m). If you like Sanchez at 11.9m then who is the forward who balances the equation for 8.1m? Vardy is close enough in price to be doable, as is Firmino, and then you have the next group of the likes of Rashford and Welbeck (though you likely wouldn't want to go double Arsenal). This model isn't perfect of course, but, accepting it's limitations, and looking at that group you see players projected for somewhere around the 60 point mark, a full 20-30 points behind the elite forwards. That puts a lot of pressure of Sanchez to make up the difference given that the likes of Salah, Silva, Eriksen and Alli all bring a similar level of job security and are looking at points hauls of around 70 themselves.

Based on the above - very rough - maths, Sanchez would need to be getting into Kane-level returns to justify his premium price above those other top midfielders and that's hard to project right now. Of course, you only have to go back to last season so see such a level of performance and if any midfield option can do it, it would surely be Sanchez, but I think the conclusion for now is that we need to see this week's performance level and maybe more over a couple of sustained weeks before he makes logical sense, although for those looking to gain ground on teams already, he offers a rare opportunity to own one of the best handful of players in the league without sharing his inevitable returns with everyone else.

Shane Long
In some ways the elite players in the league can seem to cancel each other out, either because a huge portion of fantasy managers own them, or because they offer equally good value to another option who costs a similar price (see the recent Kane vs Lukaku vs Aguero vs Morata contest). Where you can make a sneaky difference is around the edges of your first team: players who need to play almost every week but need to come at a discount price. I'm not sure he's there yet but Shane Long's appearance in a prominent place on this week's chart highlights the Irishman's return to favour at Southampton and continues a decent run in Pellegrino's side. Over the past three gameweeks Long is tied with Aguero and Kane for the most touches in the opponent's box (22) and has racked up 7 SiB, just one behind Lacazette and Vardy and two behind the all conquering Kane.

There is some concern around the quality of those shots but for what it's worth Understat ranked his xG for this week's game as 0.54, exactly the same as Kane against Huddersfield, so it seems at least some of the shots were quality. I still like Calvert-Lewin and Joselu's potential in the budget group but not one is doing a great deal to stand out right now which opens the door for someone like Long to get a look in if Southampton can get back on track in the next month which features games against NEW (H), WBA (H), BHA (A) and BUR (H).

*After writing the above I now see that Long missed tonight's Ireland v Wales game, so obviously check his status if you did want to make a move.

Richarlison
Not a great deal to say here, other than that it's amazing people aren't on the Brazilian yet. To date 90,000 managers have brought him in - which isn't nothing - but it's less than the 97,000 who have opted for his teammate Doucoure, who has exactly 3 SiB and 3 SoT on the season (albeit all of which have become goals). Richarlison meanwhile is 2nd among midfielders in touches in the opponent's box, total shots and SiB. Even his 10 CC isn't terrible for a mid-level player focused on scoring rather than setting up others (ahead of Salah and Mahrez and tied with Willian).

Watford get Arsenal this week then face a tough trip to Chelsea so perhaps managers are wisely waiting until after that to pickup Richarlison but I urge you to keep him in mind at that point, even if he's kept quiet for those tricky games, as Watford then face only two really tough fixtures in the next 12.

Kevin De Bruyne
I have heard some talk that De Bruyne is widely considered to be the best player of the 2017-18 season as we approach the quarter-way mark. I am not particularly interested in debating that suggestion but I am interested in this kind of discussion's impact from a fantasy perspective. A player's overall ability is not a huge concern for fantasy purposes - other than I suppose the small impact on earning bonus points - but rather it's simply about racking up goals and assists. In terms of assists, there are few, if any, better placed that the young Belgian. He leads the league with 24 CC and with elite teammates getting on the end of them, not to mention a large chunk of them coming from set pieces, from which De Bruyne clearly excels, there is no arguing his assist potential is sky high. However, his teammate Silva trails him by just a single created chance and has notched six "big chances" created to De Bruyne's three, most likely due to the advanced areas behind the front two that Silva has been occupying of late. Either way though, let's call it a tie.

The goal threat however is far from close. Silva has racked up 9 SiB with 3 "big chances" in the first 7 gameweeks, compared to just 2 SiB for De Bruyne and 0 big chances. Of course, the Belgian has 12 efforts from outside the box and will no doubt ripple the net a couple of times this year thanks to his quality, but history shows that SoB are converted at a low rate, even for a player of De Bruyne's quality. Consider that last season he converted 54 SoB in 4 goals (a 7% rate) and the season before that he notched 2 goals on 27 SoB (7%). This season he has a single goal from 12 SoB for, you an 8% conversion rate. This puts him on track for something like a 5 or 6 goal season if he plays every week. Now, the retort could be that Silva is yet to find the net at all, but give me the player who's shooting from inside the box will regularity and has averaged over 5 goals a season over the past three despite playing just an average of 26 games any day of the week.

Factor in Silva's 1.5m lower price tag and I find it hard totify De Bruyne's 17% ownership. In fact, I could make a decent argument he's the 4th ranked City midfielder I would own, given the additional chances Sterling and Sane should get in the side with Aguero sidelined.

Saturday, October 7, 2017

Wilcard resources

As we sit in the middle of another dull international week, many managers will be tempted to play (or have already played) that wildcard chip.

With that in mind, I wanted to link to a few resources that I have posted over the past few weeks that might be useful

Overall player projection - projected points for the next 12 gameweeks

Player share of key stats - the percentage of their team's SiB and CC that each player has accounted for

Points vs Expected Points - a quick way to highlight players who have underperformed their underlying stats to date and could see increased fortunes in the future with improved conversion rates.

Performance vs prior season - see how players have performed in this season's fixtures compared to the same fixture last season

Team snapshot and projection - which teams are performing best and who do you need to secure coverage for?

Defender selector - which defender gives the best combination of value and attacking threat within each team?

Differentiators - whose ownership numbers remain surprisingly low?

Finding a differentiator

One of the downsides of the premierleague.com fantasy game is the fact that every manager has the same access to every player, which can cause teams to converge as the season goes on. This can lead to the conclusion that we need ways to differentiate our teams to try and gain some advantage over the pack. I would suggest there is some danger in chasing this idea too much as ultimately you need to be chasing points, not just unique points but there is of course some value to having players who offer something a bit different.

The below visualization shows the standard points vs expected points chart but with the marks colour coded based on ownership. The bluer marks are the players everyone seems to own (Lukaku, Kane, Salah etc) while the orange marks show the players flying below the radar.


The first observation is that the vast majority of players are in very few teams so your search for differentiators doesn't need to go too deep. You don't need to be looking at the 4th defender on Brighton's backline to find a variable: Monreal, for example, is the third highest scoring defender to date but is owned by just 6% of teams. The second point to note is that if you look at the ownership charts of the players at the top end of range, they are generally increasing so it's only going to get harder to separate your side from the pack.

A couple of players that stand out for me:

Richarlison (MID, WAT, 6.1m, 6% owned)
As noted above, I think people can get too cute when it comes to looking for differentiators. A team's 3rd of 4th best option might have a nice run but over a few games it's likely that their chances will start to diminish, unless they're in a truly special team (such as Sterling and Sane at City). The beauty with Richarlison is that he is arguably Watford's best player, accounting for 29% of Watford's SiB and 17% of their CC, ranking 1st and 2nd respectively (he trails Holebas in CC). There just aren't that many mid-level midfielders that excite me at the moment and so with so many managers looking to spend 30m+ up top, I am surprised there hasn't been more interest in the Brazilian. Back to back goals in GW6 and GW7 seem to have started to move the ownership needle though.

Sterling (MID, MCI, 7.9m, 6% owned)
This pick may look contradictory based on the suggestion that you shouldn't get too cute with your picks, but such is the potential of this City side, any way to access it is worth consideration. With Aguero out for perhaps 6 weeks there are additional minutes to go around, which should open things up a bit for Sterling (and Sane). Sane has of course outscored Sterling to date but his playing time has been so limited that's it hard to project anything with much certainty. Sterling is not a certainty himself but I prefer his combination of potential and playing time as an additional way to get access to the City juggernaut.

Joselu (FWD, NEW, 5.5m, 1% owned)
The Newcastle man's low ownership is a bit of a puzzle as for anyone who wants two elite options up front plus a selection of expensive midfielders, they need a cheap forward to round out their team and Joselu is about as good as anyone in terms of points to date in that group. His expected points total is even better and with a continued run in the side and a bit more adventure from Newcastle, one could see Joselu being a 8-12 goal man who can be deployed when the fixtures look best. The fact that he's the third most owned forward on his own team is a nice little bonus.

Tuesday, October 3, 2017

Individual game performance this season vs last season

Readers of this blog will likely be comfortable with the idea that one way in which we tend to mis-evaluate a player's performance to date is to focus too much on outcomes and not enough on process i.e. on goals and not shots. This problem, of course, is what stats like expected goals (xG) try to combat, as does simply looking at underlying stats rather than focusing on goals or assists.

Another area for caution is to adjust for the opponents an individual player has faced. A player may well be good value for their 3 goals in 3 games based on their underlying stats, but if those all came in games against Crystal Palace, Bournemouth and Swansea then it doesn't necessarily mean they will enjoy future success when the opponents get tougher. This is implicitly factored into the player projections, which are based on individual opponents but there are holes in the model that can need to be recognized.

For example, the model allocates a team's projected shots to individual players based on the percentage of their teams shots they have accounted for in the past, but what about the scenario where a player feasts on weaker sides, accounting for 30-40% of his team's total shots, but goes quiet against the stronger sides? This is a fairly nuanced point and one that isn't immediately obvious how to embed in a model across the entire population.

The below visualization therefore attempts to fill this void a bit, just as a sense check for how you think an individual player has been performing. Each player's SiB and CC in games this season are plotted against how they performed in the respective fixture last season. We're only showing games where a player logged more than 45 minutes in each fixture, so you won't necessarily see every game from this season on there. More marks in the bottom-right, orange section speak to a player who has been stronger against a like-for-like fixture in the current campaign (see Harry Kane's SiB) where as more marks towards the top left show that they performed better last season (see Nathan Redmond's SiB). Hovering over each mark will show the opponent and in aggregate can help build a bit of nuance as to where the player is succeeding or failing this season compared to last.

Wednesday, September 27, 2017

Points vs Expected Points: Gameweek 6


Elite forwards
It was quite a week for the league's leading forwards with five of the seven 10 million pound men all finding the back of the net at least once (the other two - Jesus and Zlatan - were not in action). Kane owners were feeling smug after his 13 point haul in the early game, only for him to be eclipsed by Morata and almost matched by Aguero later in the day, while Lacazette sent a reminder to the league that he is another talented option with a brace on Monday night.

There is an emerging theory that one must own three of these elite options, and make up the difference elsewhere in your team with reasonably priced defenders and budget midfield options. While I understand this logic, I would not be so fast to dismiss the midfield elite with Sanchez and Hazard returning to their sides and the likes of Eriksen and Salah putting in quality performances every week. The wisdom of this argument will likely only be settled with hindsight.

What we can review is which of the elite forwards should be targeted. While Morata stole the headlines, it was actually Aguero (and to an extent Lacazette who benefited from a penalty) who led the week in xP. This was perhaps to be expected given Aguero's opponent but it served as a welcome reminder that all else being equal, Aguero still likely has the potential for the most explosive points totals given the heights this City team have shown they can hit. However, the Argentine is also the most likely player in this elite group to be rotated and of course costs over a million more than Morata, Jesus and Lacazette.

Through the next 12 gameweeks the model still has Kane as a clear leader followed by Lukaku and Aguero in a near tie. Jesus and Morata are then closer behind with Lacazette trailing by some distance. There's talent there for sure but given the Arsenal man's price tag, it's almost impossible to justify taking that flyer right now. One element that intrigues me about Morata is the share of Chelsea's shots inside the box he's accounted for when on the pitch (30%). No one else in the Chelsea team is over 16% which makes you feel very confident that if Chelsea have a weak opponent and the Spaniard plays, fantasy points are likely to come your way. The same cannot always be said for someone like Aguero who not only faces increased rotation risk but also has to share the spoils with more players when he is on the field (22% of SiB). Of course, if City keep scoring 5 and 6 goals a week there will be plenty of goals for everyone but when the scoring machine slows a little, one could argue that Kane (41% SiB), Morata and Lukaku (31% SiB) offer great certainty of success. In short, I believe Kane is close to a must own but could make an argument for any of the other group and wouldn't be scrambling and spending 4 point hits to flip between them regularly.

Mid-level forwards
For those not yet convinced by the three-elite forward option, a few players this week highlighted their own potential to round out your front line. Vardy and Hernandez have both been steady performers this season and while they certainly aren't unknowns (12% and 20% ownership respectively), they are sometimes forgotten men when compared to the elite group.

I think it's too early to make a call on Bony yet, but there is a lot to like with Vardy and Hernandez. The problem is not so much these players, it's who they would be paired with. Presumably the rationale for downgrading from, say, Kane to Vardy would be to free up funds to use in midfield but of the top ten most expensive midfielders I would suggest that only Salah and Eriksen have been definite successes to date. If Hazard and Sanchez can return to form then they could offer just as much value as the elite forwards and thus a cheaper forward would be a useful, possibly essential, tool to give you access to them but until that happens it is indeed looking like the best bet might be to roll with three elite options.

An alternative idea is to go with just two truly elite options and then stack your team with a host of second tier priced players such as Silva, Mkhitaryan, Pogba, Vardy and even the likes of Sterling and Sane (see below). This protects you somewhat from rotation and makes it easy to change direction during the season, though the captains armband becomes tougher to award and if you structure your team without someone like Kane, it can take two or even three transfers to free up the funds to get him back, so you better be sure you're happy with the direction (or have a wildcard to spare).

Man City midfielders
Generally a prerequisite for fantasy consideration is being all but locked into a team's first team plans. Of course we know that the likes of Kane will still be dropped every now and then but we don't tend to tolerate fringe players who might only get 20-25 starts. Enter Sterling and Sane. The City pair rank 6th and 8th in points among midfielders and generally have the underlying stats to support their impressive hauls.

At just 7.8m and 8.3m they are competing with mid-level options like Antonio, Sigurdsson, Pogba, Rooney, Benteke or Defoe and when playing, their advanced positions in such a dynamic team will surely help them eclipse this group. Though perhaps slightly more impressive when playing, Sane's lack of Premier League experience and numerous sub-appearances still make me nervous but I am convinced that the criminally underrated Sterling will get enough time to make him valuable. You will need to secure strong bench options though - which might therefore preclude you owning three elite forwards - but I definitely think there's a way to fit him into your side and offer a very reasonably priced way to get access to this talented City side.

 After this week's trip to Chelsea, City's fixtures are extremely promising and I would definitely consider having Sterling for 9/12 of them rather than many of the above group for 11/12 of their games.

Monday, September 25, 2017

Player share of key stats, by team

The below visualization shows the share of their team's shots inside the box (SiB) and created chances (CC) each player have accounted for this season. The share represents only the games when the player was on the field so as to not penalise them for missing games. This also therefore means that the total team percentage will not add up to 100%.

While shots inside the box are generally more valuable than those from outside, this data does not control for quality beyond that, so an overly trigger happy player like Andy Carroll might appear more valuable than he is, while a clinical finisher like Aguero might be underrated. Still, the idea here is provide a quick sense check as to where players rank within their respective teams.

We often see people cite team A's superior fixtures to team B as the key reason to select player A over player B, but this misses the impact of the likelihood of these players benefiting from their team's favourable fixtures, which I hope this player share data can help with a bit.

Tuesday, September 19, 2017

Elite forwards: a response to City's past week

Over an eight day period last week, Man City thumped their three opponents by a combined score of 15-0, with Liverpool, Feyenoord and Watford unable to contend with Guardiola's men. It goes without saying that City were extremely impressive in these games and fantasy football managers are obviously taking note with Aguero and Jesus shooting to the top of many managers' transfer target lists (at the time of writing some 440,000 managers had already brought in Aguero and another 90,000 have targeted Jesus). The point of this post is not to suggest that these transfers are incorrect - indeed I might follow suit myself - but I did want to run over a few facts to maybe turn the temperature down on the need to make these moves right now.

The chart below shows the expected points each of the listed elite forwards have registered through the first 5 gameweeks. You can see Aguero's terrific GW5 effort eclipsing his rivals this past week but you will also note that Kane has three gameweeks with an expected points total close or above Aguero's game against Watford. Now, it should be noted here that the expected points number I am using is not as complex as some models, and indeed is a simplified version of my own, but it does a good enough job highlighting that Kane and Lukaku have been wracking up very solid shot and created chance numbers on week-on-week and so one very good game from Aguero, and to a lesser extent Jesus, does not need to completely change your transfer plans.

Note: Firmino's sky high xP in GW1 is due to his penalty which is scored in the model as essentially 4 guaranteed points on top of his other goal and assist potential.

The model forecast still likes Kane quite a bit more than any other forward using the blended or prior year season conversion rates, which ranks Lukaku just ahead of Jesus and Aguero in terms of projected goals. Aguero tops all his rivals when it comes to assist threat which is a useful tool to have and would push him sufficiently far ahead of Jesus as to justify the extra million or so pounds.

To me, there remains a relatively clear hierarchy of Kane at the top, Lukaku and Aguero in a near tie for second and then Jesus, Morata and to an extent Firmino following in the lower tier. Therefore the switch from Lukaku to Aguero makes good sense but is not suddenly a "must do" transaction if there are other areas of the team you need to address.

Friday, September 15, 2017

Gameweek 5 Projection

Note: I have still not figured out a method to allocate clean sheet points to players that I'm happy with, so for now the below projection is for attacking points only (plus two for playing time). Clean sheet forecasts can be found in the team projections here.

Friday, September 8, 2017

Revised player forecast

One of the key complications with player forecasting - or indeed I imagine any forecasting - is deciding which data set to use. When it comes to fantasy football, we obviously want to include as much recent data as possible but the issue is when we can exclusively rely on this season's data and when we need to look to the past seasons for guidance. I am generally quite happy to solely rely on this season's raw event data such as shots or created chances fairly early on as they tend to occur with relative frequency and thus stabilise in a short time frame. How these events get converted into goals can fluctuate a lot more though, as the key driver there - goals - happen much less frequently. With this mind, the revised player projection table below allows you to choose how you are converting the raw chances into goals and assists:

  • Past season - uses the benefit of having a 38 game sample to see how different teams convert chances into goals. The negative, of course, is that teams have changed since the previous season, both in terms of personnel and with the arrival of three new promoted teams (who use a historical average for promoted sides in this forecast);
  • Current season - the most up-to-date conversion rates will help to spot players and teams who have genuinely improved since last season but will be subject to a much greater sample size risk so will kick out some unusual results;
  • Blended - this rate uses a combination of historic and current data, increasingly weighted towards the latter as the season progresses.
A couple of highlights below that jump out as of gameweek 4:
  • I generally dislike the term "must own" as there are thousands of ways to build a successful team but there is no denying that Kane's data so far this season is simply incredible. The fact that his ownership percentage has fallen to 26% - including a 0.1m price reduction - represents a great opportunity and it's hard to see how one could select a wildcard team now without the Spurs man.
  • Mahrez is an interesting case of low ownership with just 5% of managers fancying the former Champion. Perhaps this was due to the presumption he would leave Leicester during the transfer window, but now that is closed, a lot more attention needs to be directed his way. Using the prior season conversion rate cuts his xG significantly which reflects the fact that Leicester have been so clinical (lucky?) this term, but nevertheless he remains a legitimate elite midfielder who at 8.5m isn't too badly priced.
  • The xA listing offers more moderately priced options than the xG list, which makes me wonder if it will be better to focus resources on elite forwards and midfielders who can score goals, knowing that you can find low-risk-high-reward midfielder picks who contribute assists with cheaper options like Brady, Carroll or Loftus-Cheek.
  • With Spurs offering about as good defensive prospects as any team, the fact that Ben Davies ranks so highly in xA while also being cheaper than most of his teammates makes him a very promising prospect.

Select tabs below for goal and assist forecasts for the next 6 and 12 gameweeks:

Saturday, September 2, 2017

Expected goals, assists and points

The visualization below plots the expected fantasy points arising from expected goals versus those arising from expected assists. The idea here is that this is a quick snapshot of how a player has performed to date and where their points are coming from. It should be noted that xG and xA numbers used to generate the xP are based on shot, created chance and possession date for the 2017-18 season only but the conversion rates to convert those raw events into goals are regressed using team and league rates for both the current and prior seasons. I hope this eliminates some noise from the small sample sizes of the early season but it's still worth noting that this is a snapshot based on three games so should act as a data point for your transfer assessments but not an all encompassing answer.

Friday, August 25, 2017

Some help to pick your defenders

Quick note: One of the reasons I restarted the blog this year was that my wife and I were expecting twins in late September so I knew I would be home a lot more with plenty of sleepless hours available to mindlessly consume football matches. Well, the twins didn't think this was a great idea and decided to convert xTwins into Twins on August 13th. This means I've been a bit delayed rolling out some of the models and ideas I had to kick off the season but once we get into a routine I will ramp up the content a bit. I like to think that they are already concerned about the potential issues around small sample sizes and wanted to force me to wait until the season was a few weeks old before overreacting.

Selecting defenders and 'keepers requires a different strategy to your attacking options, given that so much of their value is locked up in their team's performance. Of course, playing on a good team will help any player but while it's possible to have a lot of success as a forward or midfielder on a mediocre team, it's really hard to do so as a defender, barring a freaky season where you get extremely lucky with goal conversion or are fortunate enough to be played higher up the pitch.

Thus, with a few exceptions over the years, I tend to pick the team first and then figure out who offers the best way to access that unit. This will require a weighting of three factors:

  • playing time
  • price, and
  • attacking threat

Generally you will want to ensure the playing time factor first and then weigh the attacking threat against price tag and see how much bang for your buck you can get. Hopefully the below viz allows this to be done quickly for each team. Let's run few a couple of teams below to get an idea of how I hope it might work.

Note: The data within is based on the 2017-18 season only and thus needs to be taken with all the relevant small sample warnings. If you have a significantly higher or lower opinion of a player's attacking ability then don't totally discount it, but this might serve to adjust your prior, especially once we get another week or two under our proverbial belts


Brighton
Let's start with an easy - if somewhat theoretical - example. I must concede here that I haven't seen Brighton play a full game this season so this is a theoretical pick for illustrative purposes. Chris Hughton has picked a consistent back four in the first two games, all of whom cost 4.5m so if you wanted a Brighton defender you should simply be looking to maximise attacking threat, which to date points to Lewis Dunk by a reasonable distance. Suttner's 11 passes in the final 3rd point towards a player who might create chances in the future but otherwise the pick here should be Dunk. If these numbers hold up then it would start to suggest that holding other Brighton players would be a mistake.

Southampton
The first thing to note here is that Bertrand comes at a premium to his teammates yet, at least so far this season, actually has a lower attacking threat than both Cedric and Yoshida. Now, in this particular case I think one might want to exercise a bit of caution as Bertrand has a decent history of delivering solid attacking returns, but if this trend continues then it makes little sense to own the former Chelsea man. The data would suggest that Yoshida is an interesting differentiating option as he's provided the same attacking threat as Cedric but is owned by just 2% of managers compared to Cedric's 12%.

Chelsea
David Luiz's performance last week in midfield received good reviews which makes him well placed to earn minutes in this team. At just 6.0m he brings with him a good attacking threat which in theory then renders Cahill, Azpilicueta and Rudiger as poor investments. The question then becomes how much better Alonso is and whether that gap justifies the extra 1.0m. If you are aiming for a 2,200 point season then that 1.0m will need to earn you somewhere in the vicinity of 22 points (this gets more complicated later in the year, but bear with me for now) which is a goal and a handful of assists or 3-4 goals. That's a fairly significant haul and so while every else dives on Alonso after last week's heroics, I would suggest that the decision is closer than it looks.

With just two gameweeks in the bag, it's hard for players to really start to distinguish themselves from their teammates but I hope this little viz will be useful in the coming weeks as you look to structure your defense, perhaps during a wildcard international break.

Sunday, August 13, 2017

Model Behaviour: Converting shots into goals

Thursday, August 10, 2017

Model behaviour

As democracies teeter on the edge of existence around the world and once-eradicated diseases return due to an apparent loss-of-uptake of vaccinations, we appear to be in a time where the masses are losing faith in experts. Scientists, journalists and those steeped in the scientific process are being drowned out by those who "go with their gut" and follow their id. I am here to stand up for the experts, though alas, I am not one. Those more learned than I will quickly realise that this blog is the work of a child in his father's suit trying to close business deals (actually, that might work these days).

Still, you've made it this far so you might as well stay for a bit of analysis, even if my statistical base knowledge is formed from watching archived Harvard lectures and reading old Fangraphs posts. 

For those just joining us, I ran this blog for a number of seasons but took last season off. I have built a reasonable, though hardly sophisticated model to try and project fantasy football scores and I hope you'll follow along this season as we see where we get things right, and where it all goes horribly wrong.

In advance of the new season, I posted the projections for the first 12 gameweeks and wanted to discuss a few of the names to give everyone a flavour of where the numbers come from (clue: not my gut). A few readers were kind enough to share some of the names which jumped off the page as odd, so we'll start there then I'll add my own concerns:

New signings and injuries
I'll get a couple of quick ones out of the way first - h/t to @JoseMourinhoIND who asked about Mohamed Salah. All new arrivals to the league are missing from my projections for now as I don't have a statistical baseline on which to form their forecast. I have toyed in the past with trying to translate stats from other leagues - and that could be a worthy project again - but with Opta stats hard to come by for other leagues and the small sample of players who move from, say, Serie A to the Premier League, it's tough to get a forecast that I really feel good about. The new players will be added to the model as soon as they enter the Opta database but we'll obviously need to tread carefully and not overreact to a week or two's worth of data.

With regard to injuries, @GoalscorerC notes that the list includes players like Hazard and Sanchez who won't play in the first couple of weeks. This is indeed a problem but one I have just accepted I have to live with. Other responsibilities coupled with no longer being the UK just make it too hard to follow all the team news and keep an up to date list of who's in and who's out. I decided it's better to therefore permanently include everyone and outsource the team news to our friends at Fantasy Football Scout or Sky Sports.

Alli vs Eriksen vs De Bruyne
@mpok3_fpl asks why Alli is rated so much higher than teammate Eriksen and why both are ahead of assist-God De Brunye. Eriksen and De Brunye are relatively close with 53 and 49 points respectively projected for the first 12 gameweeks of the season. This pair are very similar across the board and two of the key metrics in the model - the share of a team's total shots inside the box and created chances a player accounts for - are almost exactly the same (Eriken has a ShareSiB of 10% and ShareCC of 24% versus 9% and 23% for De Brunye). Neither player takes penalties and both provide a good threat from corners so the conclusion is basically that Eriksen enjoys a slightly bigger piece of a slightly bigger pie. 

Alli is a different profile player and the model loves him. Among first team regulars, his share of SiB rate of 18% is bested by only Antonio (25%), Sanchez (24%), Redmond (20%), Arnautovic (20%) and Hazard (18%). Sanchez and Hazard are obviously elite fantasy options (and priced accordingly) and while the other names of this list are reasonably priced, remember that they enjoy a slightly larger share of a significantly smaller expected goal haul (Southampton and Stoke are forecast to score 20 goals between them in the first 12 gameweeks, compared to Spurs' 21 goal total). Alli isn't just a one dimensional player either, accounting for around 10% of his side's created chances. 

A further consideration for this trio is their shot profiles. Last season Eriksen managed to easily eclipse his counterparts with 133 shots compared to Alli's 94 and De Brunye's 86. But, Eriksen took 94 of those efforts from outside the box and converted them to goals at a 3% clip, which is right around league average for long rangers. Alli meanwhile managed 58 SiB and converted these efforts into goals at an excellent rate of 28%. In fact, this rate is so good that it might the cause of the most concern for Alli. His GiB/SiB rate of 28% and G/SoT rate of 40% are both well above league average and might suggest regression this year. It sounds obviously true, but there is at least some doubt about a player's ability to convert chances into goals at a sustainably higher than average rate, but I am largely convinced that goals per overall chance is more controllable than pure goals per SoT, which does seem to have an element of luck involved. As I continue to refine the model in the coming weeks I might look to regress these high GiB/SiB rates more than I currently do, which would hurt elite players like Alli (28%) or Sanchez (24%) and boost players like De Brunye (6%) or Sigurdsson (5%) who were less clinical last season.

How about Liverpool
Our friends over at @The_First_Touch ask about Firmino and Coutinho being surprisingly low and wonder if it's again to do with shot profile. When I first looked I assumed that the model wasn't overly impressed by Liverpool's prospects as a whole but, au contraire, they are actually forecast for the 5th best attack through the first 12 gameweeks. The problem for this pair is that they just weren't very efficient with their chances last year, even accounting for shots taken outside the box. Their GiB/SiB rates were 13% for Coutinho and 16% for Firmino, which are solid but well below the sky high rates mentioned earlier for the likes of Alli and Sanchez. So again, how you feel about this pair probably comes down to how much you think these shot rates regress. For what's worth, if we jump back another season we see rates of 23% for Alli, 21% for Firmino and just 10% for Coutinho, perhaps suggesting Firmino has some room to rise, but maybe Coutinho is right about where he is going to settle.

How to value defenders
This is the big issue for me and one I do not have a satisfactory answer to. I am fairly confident that the model does a decent job and forecasting goals conceded per game which allows for a reasonable ranked assessment of whether, say, Southampton or Swansea are more likely to keep a clean sheet this week. However, when it comes to converting this probability into points, the model (i.e. my small brain) struggles. This tends to undervalue clean sheets and thus players with good attacking stats become overvalued, especially those who have enjoyed attacking success in limited playing time (and whose rates aren't sufficiently regressed by the model). 

One option would be to simply forecast defenders' attacking numbers, which allows for comparability between teammates but is useless when deciding whether to go with defenders from different teams or whether to go with a back three or four. The other is to keep going with the deeply flawed version and try and find a better way to convert predicted shot data in clean sheet probability (suggestions in the comments!). I therefore ask that you if you see the odd weird name in the defensive listing you take it with a pinch of salt and instead primarily focus on the team defensive forecast if you want a bit of help setting your weekly lineup or planning a team's defense to back. More on this topic in coming weeks.