Scatter graphics: Premier League, 7 Sep 2022
There have been just about enough matches played for a first outing of 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).
Arsenal have joined the usual ‘big two’ of Liverpool and Man City in the dominant bottom right corner, while newly-promoted Bournemouth appear to be struggling: they’ve been out-shot almost 3 to 1 so far.
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:
There are a few profligate attacks stretching things out at the moment, with Wolves enduring a terrible conversion rate despite creating an average 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:
While Wolves are struggling to put the ball in the net they’re at least making it almost as difficult for their opponents to do so: no team has soaked up more efforts for each goal conceded. Leicester meanwhile have the division’s leakiest defence.
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, Arsenal are still mixing it with the ‘big two’. Liverpool have looked the most dangerous in attack despite some mixed results, while Man City‘s defence is the toughest to crack.
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