Wednesday, September 5, 2018

Comparing like-for-like fixtures and underlying data

As noted in other recent posts, it can be hard to know what data to rely upon in the early gameweeks. We all know that shots inside the box or those on target tend to correlate well to goals, but with only a few of those events happening each week, it can be easy to overreact to unstable data. One data point I am interested in, is how well teams are doing compared to same fixtures from prior season. This data is still fraught with issues - teams might have changed personnel or have injuries or simply suffered a bad game - but we at least have a baseline to compare against which gives a little more context to what we're looking at.

The below visualization shows the Goals (G), Expected Goals (xG), Shots Inside the Box (SiB), Created Chances (CC) and Successful Passes in the Final Third (P3rd) for each team's fixtures for 2018-19 (CY) compared to the same slate of games from the 2017-18 season (PY). We'll highlight a couple of the more interesting observations below the viz:


Chelsea
Of the four games Chelsea have played to date, they drew a blank in three of them in the corresponding fixture last season. Their combined xG over those games was 3.0 - so there's no doubt they were a little unlucky to come up empty - but still, the difference between that streak of zeros and this season's 7 goal haul (with an xG of 4.3) help to underline the potential improvement we are seeing under Sarri. They doubled their SiB in two of those games and have come close to tripling the number of passes they have completed in the final third of the pitch. Looking at the opponents doesn't appear to completely explain this improvement either. Ignoring Huddersfield, against which Chelsea played just about as well as last season, we find Arsenal who one could argue are still finding their feet under Emery but are otherwise largely unchanged from last season, a Newcastle side that is largely unchanged and gave Man City a good game this past weekend, and a Bournemouth side who appear stronger than last season.

The pressure that Sarri's team is going to create with so much possession in the final third is surely going to be too much for some sides, and while one can argue how that translates into wins and losses, in fantasy terms it creates more chances, which typically lead to shots and points over the course of a season. Chelsea's lineup make it somewhat difficult to load up on their players, as you might do with, say, Mendy, De Bruyne and Aguero at City, but this improvement makes Hazard extremely appealing and I think justifies doubling up the Belgian and Kante, or even Pedro (though I fear too much rotation with the latter with Willian also available). If Morata could find some form and develop under this system then he too might play his way into contention before the year ends. We've already discussed how Alonso appears to justify his price tag - at least compared to his Chelsea colleagues - and nothing here seems to contradict that fact.

Liverpool
Liverpool have the worst differential between the goals they've scored in the four games this season versus their haul in the same fixtures last season. Of course, before you immediately start planning for how you're going to divert your 13m Salah funds, consider that the baseline they have fallen from was impossibly high - 13 goals in 4 games - and if you look at their xG they are actually much closer with 9.3 xG for this season compared with 10.4 xG for last. That said, a quick peak at the underlying data does show some drop beyond just unfortunate timing with a significant drop in both SiB and CC. I don't think this is anything close to being a cause for concern but it might be a small factor when considering whether to sell Salah for a few weeks during this tough run of games: if the heights aren't quite what they were last year then it becomes less scary to sell the Egyptian and use your funds elsewhere with a reduced fear of Liverpool massacring sides and earning huge points totals for their players. For what it's worth, I am considering moving Salah and Alexander-Arnold for 4 gameweeks, given the fixtures and the fact that neither have seen a price rise to date that will make buying them back a big issue.

Leicester
Leicester's stats are interesting, though I'm not sure what they mean from a fantasy perspective. Their xG and SiB are down around 40% from the corresponding fixtures last season, and that has played itself out in the goals column, that has decreased from 6 to 4 (they did of course manager two against Wolves which is excluded from this analysis, so let's not be too harsh too quickly). Their passes completed in the final third have doubled though, which suggests increased attacking possession. I don't see enough Leicester games to conclude that this is an intentional strategic shift or whether it's due to Vardy missing a couple of games (and with him that ability to counter so well), but it's something to watch going forward as it could shift how different Leicester assets are valued in this side. For now though, I want to see a return to form when Vardy is back or else fear this side might offer little fantasy value this year.

Man Utd
This data might prove to be some relief for Man Utd fans, given that the majority of the news about their club seems to suggest the sky is falling. After struggling to generate shots in GW1 and GW2, United doubled the number of SiB against TOT and BUR that they managed last season, and saw their xG rise from 1.6 to 4.0 in those two games. Their completed passes in the final third took an almost unbelievable drop against Leicester and particularly Brighton, to the point I had to go back and check the data but based on what we've since seen against Spurs and Burnley, the outlier wasn't so much those games this season but the corresponding fixtures last season where United were able to dominate possession against weaker sides, albeit not always to great effect as United of course went on to lose that game to Brighton. I'm not exactly sure what to make of this fact. Are United more clinical, luckier, or just playing a different way? I think we need a few more games from this team to figure out what they are and which, if any, of their pricey assets might be able to contribute to our fantasy teams.

Brighton
It's too early to write teams off, or even be overly "concerned" about their prospects for a long season ahead, but the early data for Brighton is not as promising as one might think given their win over Man Utd and a close loss to Liverpool. Their created chances and shots inside the box have fallen off significantly from last year, and while their xG looks not too bad, it is being propped up by the penalty they earned against United (worth 0.79 xG). Now it's not necessarily fair to just arbitrarily take that penalty away as they did indeed earn it, but just to note that without it, they'd have an xG of 1.8 over three games in which they managed 3.3 xG last year. Again, we're not close to worrying yet or taking away credit for the penalties, but of they were indeed events of luck rather than due to a repeatable skill on Brighton's behalf, this might be of note of caution to those starting to look at the likes of Pascal Gross for fantasy production based on his team's prior season performance.

Everton
It's not a spectacular improvement but Everton have improved pretty much across the board in their three fixtures to date (we're excluding the GW1 effort against Wolves in which they also notched a couple of goals, albeit perhaps a bit fortuitously). They haven't played the toughest run of games of course, but the idea behind this analysis is that is allows for like-for-like comparisons and on this basis, the team has clearly developed. With injuries and suspensions impacting Walcott and Richarlison and Tosun and Sigurdsson yet to attract much attention, it's possible that people might start to forget about Everton, but the data here suggests they have the makings of a good mid-level team that might be a source of reasonably price squad players.

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