Scatter graphics: Championship, 2020-21
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).
Champions Norwich comfortably out-shot the rest of the division but allowed a relatively average number of chances in return. Brentford once again looked dominant in shot terms, while Bristol City allowed almost twice as many shots as they created themselves.
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:
Bristol City may have created far fewer chances than anyone else but few teams were more clinical at converting them. Meanwhile Nottingham Forest struggled in front of goal despite creating a respectable number of opportunities.
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:
Watford‘s return to the Premier League was built on a resilient defence which absorbed more than 16 shots for each goal conceded. Norwich and Swansea can also thank a streetwise back line for keeping them in the promotion race.
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, Brentford can feel understandably hard done by as their balance of chances was almost identical to champions Norwich. While Wycombe‘s defence struggled to contain their opponents, their attack didn’t look out of place at this level. Bristol City look as though they’ve got a lot of work to do over the summer.