Scatter graphics: Championship, 27 Nov 2017
Here’s another update to the scatter graphics, which compare the attacking and defensive performances of every team in a division. Each of the four graphics is explained briefly below and at length here.
First of all, here is how the number of shots taken by each club compares with those they face in return. The average number of shots taken per match is on the horizontal and the average number faced is on the vertical, so bottom right (take plenty, allow few in return) is good while top left (take few, allow plenty) is bad. The stripes are like contours: the greener the stripe, the better the performance (and vice versa for red).
This doesn’t look how I expected it to: everyone’s clustered in the middle, apart from Brentford throwing the kitchen sink at opponents and Burton doing the opposite. It’s been no surprise to see the Bees steadily climbing the table and it looks like they should still be targeting a top half finish.
QPR – who salvaged a draw against Brentford last night – also look to be in a false position in the bottom half of the table given their above-average showing here, while Ipswich‘s presence in the top half looks as though it might be temporary given how often they’ve been on the back foot.
Now let’s look at attacking alone. The horizontal axis stays the same as in the graphic above, but now the vertical shows the average number of shots needed to score each league goal. Therefore bottom right is good (taking lots of shots and needing fewer efforts to convert) and top left is bad:
Brentford may be taking a lot of shots but they’ve been somewhat wasteful so far – Ipswich and Sheffield United have outscored them despite taking around seven fewer shots per match.
There’s also a hint at why Ipswich are doing so well despite creating relatively few chances: they’ve been ruthless in front of goal so far, with just over six shots taken for each goal scored.
Wolves are even more clinical – in fact over twice as effective at Norwich at converting shots into goals despite the Canaries marginally out-shooting them – while Birmingham‘s woeful shot conversion is bad enough to make me suspect that they’re due some better luck in front of goal.
Next let’s look at the defensive situation – basically take the above chart and replace the word “taken” for “faced” on both axes. Now top left is good – facing fewer shots and able to soak up more per goal conceded – and bottom right is bad:
Cardiff‘s promotion campaign looks to be built on their solid defence, with Aston Villa and Wolves also looking pretty strong at the back.
Brentford seem to have a similar problem in defence as they do in attack: they’ve nailed quantity but not quality, a bit like Liverpool in the division above.
It’s been a frustrating season for the back lines of Sunderland, Hull and Bolton, who have all allowed a respectable number of chances but seen the ball fly into the net with depressing frequency.
Finally here’s an attempt at correcting the first graphic for the quality of chances created and allowed, using the same “expected goals” values that power my shot timelines (explained here). The reason for doing this is that the results tend to correlate more strongly with performance than when we treat all shots equally:
When we correct for shot quality, Wolves shoot into the bottom right corner with Cardiff, so the top two in the league table look to have earned their places. This neatness extends across the top five, with Aston Villa, Sheffield United and Bristol City not far away.
This makes Brentford‘s absence from the top half – never mind the top six – all the more mysterious. I wouldn’t be surprised to see them and Ipswich drift towards and ultimately pass each other as the season goes on.
While Burton and Birmingham‘s struggles are rendered less mysterious by this chart, there’s hope for Sunderland who don’t look anywhere near as bad as their current league position.
I’m a bit worried about Hull‘s defence – that’s a surprisingly high level of chances for a newly-relegated team to be giving up.