Sunday, 24 December 2017

Half Season Premier League shot analysis

Hard to believe it is just a month since I wrote a 12 game review. The crazy Premier League schedule continues, unrelenting in the face of cramming a season in before the World Cup. As such, there is a literally a window of today or tomorrow (might be busy) to write this, so once more you get a quick scree with some light jokes, snark and stats. Same deal, we're looking at seasons from 2009-10 onwards, because that's where you can publicly access Opta shot data. So every ranking is out of 180, which is just about large enough to make the outliers interesting.

Also huge criticism of the Premier League is deserved for scheduling the week 3 games to be the same as the week 19 games. This means that Liverpool and Arsenal have played twice already and we've not even started the second half of the season. Any analyst worth their salt can join me in shaking their head at this thoughtless scheduling. What a jerk move.

A habitual aside on expected goals. I think generally people experienced in the field are unconvinced about the reliability of any expected goals model before somewhere between 2011-2013 (depending on taste). As ever, it's easy to say "you're talking about shots, but where were they taken from" and feel smug--which is the oldest criticism against pure shot analysis there is--but you'd be missing some of the power of what shot analysis does provide. We can go back nine seasons for the benefit of this analysis, and well, if you want more detail, you're welcome to delve in yourselves! Volume is still the primary indicator, so let's see what we can find out.

Man City

Not to labour a point but everything starts with this ridiculous City side. They were 11-1-0 at the 12 game mark and now they are 18-1-0. This significantly separates them from every team on the list, apart from perhaps last year's Chelsea side who were 16-1-2 at this point and similarly riding high off a ludicrous win streak. They didn't have the bravura attack of this City side so didn't get the same superlatives. Defence was their bedrock, and sure enough they converted from here. City will convert too and they have an attack for the ages to meld to their defence. They could actually be genuinely quite bad for the rest of the season and still sail in to the title, but there's little sign that that will happen.

So how are City good?
  • Tied =1st/180 for shots on target (7.7/game)
  • 1st in shots against (6.1/game, margin is +1.5, Liverpool this season is second)
  • 1st in shots on target against (2.0 per game, +0.5)
  • 1st in total shot ratio: 74.6% (about 5% ahead of any other team, again Liverpool 2017-18 is second)
  • 1st in shot on target ratio: 79.3% (over 6% ahead of any other team)
All this feeds into this lot:
  • 1st/180 in goals scored after 19 games (60)
  • 1st in goals against (12)
  • 1st in shots on target per shot (42.8%, the kinda metric that could cool)
  • 1st in goals per shot (17.6%, 1.5% ahead of anyone else, and again usually the kind of metric you'd expect to regress/revert/cool)
So the perfect storm of rock solid structural metrics, and a smidgen of red hot conversion. It's too early to get the bunting out and talk "Invincibles" (not that it's stopped anyone...) but City have put together probably the best half season of league football this decade, century, ever? I don't know, but it's been electric stuff and for the benefit of this analysis, City is best. Rotation (as I wrote here) and easing off to pursue other goals may be the two main factors that affect any quest for perfection but they really will want to stay in the Champions League or it could be cigars and dreariness by mid-April, y'know a bit "Bayern under Pep". The perils of being too good, huh?

Man Utd

The surface outlook of Man Utd's season is pretty good. They're second in the league, well qualified for the Champions League knockouts and only ever lose at Old Trafford to Man City. However, underneath the glossy exterior is a whole world of potential trouble, at least there will be if they don't fundamentally improve. For an extended take, see my report at The Ringer, but the bottom line is this is a team that is taking 52% of the shots in its games and... wait for it... that's fewer at this point than the Louis van Gaal years (55 and 54% at this stage). I and many others gave them shit for not being good enough then, so why on earth would I stop now?

What's the matter? Last season United were taking 64% of the shots in games, but had been stymied by getting stuck drawing a ton of games at home and battering on the door to no avail. Hence the wealth of shots. This season, they've taken the lead a lot and have played more pragmatically when leading, and this has moved the needle downwards.

So, under Mourinho, they have played hard and turned it on when needed and throttled right down when they didn't? That's fine, right? Well, yes and no. If we scrappily take a mid-point between what we're seeing when things go Utd's way (we will get to this, they really have) and when they don't (this time last season), we find they spec out as a fringe top four side. 

There is a tension between two things at the back:

1. David De Gea is great
2. No human alive can long term keep the ball out of the net at the rate he has this season

He's saved over 83% of shots on target he's faced this season which is around 3% ahead of any other half prior to this year, so 1st of 180 (Burnley are on around 82% themselves, it's a miracle!) Also the full season record is ~79% for a couple of Ferguson Utd teams (2009-10 and 2011-12) so on balance, you'd expect that to be the highest they could get to (Burnley too!) as the season progresses. What does that mean in real terms? It's far more likely that Utd (and Burnley!) keep the ball out of the net at more average rates as the season goes on. These are nice stats to ride but unlikely to be a portent towards a similarly miraculous future.

At the same time Utd's attack is so hot it burns; they're scoring over 44% of their shots on target, behind only er... Watford (?) from this season, so 2nd of 180.  (Our old friend, and much maligned, but still a decent ready reckoner, PDO has them at 128 for this half season and the next best out of 180 teams is 122. Utd are 14% higher than any other of 180 teams here at this point, which is nuts). It's flaming fire at both ends from Utd without the structure you want from a challenging club to back it up. 52% of the shots remember--"Name other half a season 52% shots teams"-- okay: Palace 17-18? Moyes at Utd? Pulis at Stoke 10-11?

"Mourinho is pragmatic" is one take but I'm not so sure, what is their identity? What kind of football do Man Utd play these days? It still feels like they are firmly in transition with individual brilliance bailing them out, but are they an effective team? Time will tell, but i'm betting on a second half of the season drop off.

Don't believe me? Check out this chart from Objective Footy, which represents the two highly fluctuating and non-predictive metrics I've just described:

Yep, that's Man Utd floating happily in the top right hand corner, and the white space between them and the bunch signifies the journey they are about to take.

Also note Burnley frowns.
And Watford shrugs.

There's a lot of talk about teams--mainly Burnley-- doing special things that move their needle, and it's important to my mind to recall that while that is almost certainly true (see Pulis' Stoke etc), when everything also goes a team's way, it can significantly distort that effect, and hoodwink people into thinking magic is at play. There will be teams that are deploying tactics every bit as shrewd as Burnley, but if they haven't also picked up the breaks, they may look utterly normal to surface analysis. As ever, keep digging, but don't get fooled along the way by variance, and recall too, Burnley's defence might be doing cool, effective things, but their attack is awful (lowest xG/shot of last 5 seasons).

What else?

"Tottenham aren't as good this year" not a take I can subscribe to. They look like the same damned Tottenham side at this point they have for the last two decent Pochettino years. Very good shots team, this year they've dropped to league average on saves, which might mean they're a win or so out of last season's returns at this point. Big picture: they are the same team, doing similar things in a similar way (for all the tactical tweaks), they just haven't found the positive skews to steer them higher--yet (2015-16 had weird high accuracy, 2016-17 had ballooning conversions). Fret not, your Tottenham team is as it ever was, it's just not quite the shiny new toy/novelty it once was.

"Swansea are awful"

That they are. Still the worst attack on record for shots (8.5 per game, 180th/180) and shots on target (2.0 per game, 180th/180 by a huge margin, 0.6 per game). There was a great tweet the other day:

What else could be done? Maybe he lasted so long cos he looked nice; an urbane gent who wore a suit well. That's what managers should look like, right? Regardless, their 27.5% of shots on target in games at this stage is also 180th/180 (bad feeds bad here you see) and the rate of their already league worst shots that land on target is also 180th/180 (23.5%). Also, as if that wasn't enough, they have a weird skew where they can't land shots on target but their opponents can. West Ham last season were super weird by this side metric, and just had to improve (they did, and ranked 180th/180 at this point). Swansea are at 179th/180 so presumably can hope that there is some reversion available here, for all that is like finding one cup of water in a desert.

It's an abomination, and huge improvement is needed to drag them from the mire. From the outside, it doesn't look like they have the quality in personnel to do it and their managerial appointment will be fascinating. And maybe they should listen to Altman a bit more (or maybe not? You decide!)

"Palace are bad"

Aye, they never were and this was one of the more solid analytics/stat takes even from early on. And now they spec out as quite good; remember their shot ratio is higher than Man Utd. Roy Hodgson has little to worry him.


Same as always, electric attack: 69-70% of the shots in games this season and last (seasons rank 2nd and 3rd/180 behind this season's City team), converting at a decent clip: 12-13%. Very few shots at the other end, 7.6 a game this season, 7.7 a game last season (guess what! 2nd and 3rd/180 behind City 2017-18). And by way of contrast a shit-ton of those shots landing in the net, 16.0%, and 179th/180. This hasn't moved since the 12 game mark and Liverpool remain somewhat enigmatic. They remain like a tin of Roses, most of what they are is tasty and admirable, but who continues to sanction the coffee creams?


Shot rates are better than any recent season, save and scoring rates are down. It could well be that these factors are interrelating, but i'd be tempted to be positive about the 66%+ shot metrics and hope the 10% conversion gets a boost later. It's a balancing act, and perhaps Arsenal are just the same damned Arsenal team they always are (funny how often that seems the way when you look at seasons of data) and it'll come out in the wash. They are no worse though, so that's something, and they could be better! (Rejoice!)


Are worse. Year to year, shots are down, goals are down, more shots against. They've gone from 50% of the shots to 45% to 40% in consecutive seasons. Jermain Defoe is out for 8-10 weeks, so will be interesting to see which direction they trend now... *whistles*


Look remarkably similar to last season in all shot related stuff, and pretty good (69% of shots on target both years is excellent), just with a clip of about 0.5 goals per game lost off their attack. That's likely variance talking, and otherwise they remain solid if unspectacular. It's just that blend powered a title last time round, and it really won't this.


Are weird, because all their metrics are horrible, and likely won't move very far with the Big Sam brigade in town. But the Sam Magic Wand will get results from horror metrics, while the Koeman Kalamity got none.  All their issues remain fundamentally terrifying with fortunes squandered and an odd unbalanced and bloated squad. 12th place forever is the new 7th place forever, maybe.


Are the same as Leicester 2014-15 and Leicester 2016-17 for the most part. I appear to have mislaid other seasons for them, so we will skim over that. Forty-something percent of the shots and an occasional positive bounce. It's all very Leicester.


Worrying drop off in metrics here. Last season they were looking like a top six contender in waiting taking 63% of the shots on target at this stage, and it wasn't the first time they had done that--57% to 63% the previous three season-- but in 2017-18 they are taking 38% of the shots on target. That's a huge drop. It's as if their for and against metrics of the last four seasons have flipped and it's becoming harder to cite them as the blueprint change-resistant unit they normally are. Feels like they have the talent to do better but Mauricio Pellegrino's tenure is more Adkins than Pochettino right now.


Are super weird. 1st/180 converting 47.4% of their shots on target, of which they take very few (3.0 per game, bad 169th/180) and they are saving very little of those that come the other way (60.4%, 167th/180). So nothing is being stopped at either end. If any team is a coin flip for top half AND relegation, it's them. They've lost 8 of their last 11 after all.

Apologies if your team missed out (Stoke, worse than usual but I wrote about them here, West Brom hard to analyse with the Pulis to Pardew handoff doing nothing-- no wins since August! Again I wrote about them here. West Ham's attack has vanished too, but Moyesian methods have so far against expectations done something).

Merry Christmas all!

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