Scatter graphics: Premier League, 2021-22
Now that the season is over (barring play-offs which I exclude for consistency), I can create final versions 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).
As usual it’s Liverpool and Man City who stretch this graphic out with their dominance of matches: both teams took around 19 shots per game and allowed less than half of that in return. Arsenal and Chelsea were the only other clubs who consistently out-shot their opponents this season.
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:
Norwich‘s attacking woes come through starkly on this chart. Not only did they create the fewest chances but also needed over 16 attempts to find the net on average: four more than the next worst finishers. Despite being involved in battles at opposite ends of the table on the final day, Leeds and Tottenham created a similar number of opportunities – the difference was their quality.
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:
There’s another interesting contrast involving Tottenham here – both they and Southampton allowed a similar number of attempts at their goal, but the Saints conceded far more readily. Interestingly Leicester secured a top half finish despite only three clubs allowing their opponents more chances, while West Ham qualified for European football despite facing the sixth highest number of shots.
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, we still have the same basic pattern as in the first chart: Liverpool and Man City way out in front with Arsenal and Chelsea the next most impressive. Newly-promoted Brentford were also above-average at both ends of the pitch. Wolves will surely need some attacking upgrades over the summer as only Norwich looked less threatening up front.