Scatter graphics: Premier League, 4 Oct 2021
It feels like enough of the season has passed to justify a first look at the scatter graphics. These 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).
As is traditional, Liverpool and Manchester City are dominating the shot counts, with the Reds more industrious in attack and City the more effective in defence. Leeds matches continue to be entertaining while it’s surprising to see Tottenham and Leicester having some of the worst shot differences in the division.
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:
I’ve had to stretch the template here as Norwich‘s horrific shot conversion so far was rendering the rest of the graphic cramped and unreadable at the normal height. The good news is that a record of just two goals from over 70 attempts looks unsustainably bad and is likely to improve. They’re also disguising some concerning shot conversion over at the likes of Arsenal and Wolves, who are struggling to convert a decent number of chances.
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:
Chelsea may not have restricted their opponents’ chances as effectively as Manchester City but they’ve proven incredibly difficult to breach. Wolves‘ defence deserves a mention for allowing the second fewest shots in the division, while a much-changed Crystal Palace have also faced fewer than I’d have expected given their tough start – they just need to get better at keeping them out.
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 adjust for shot quality it’s again Liverpool in attack and Manchester City in defence who are streets ahead of the rest, with neither being slouches at the other end either. Tottenham and Leicester look a bit better than they did in the first graphic – they may not have created that many chances so far but the ones they have carved out have been of reasonable quality.
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