Scatter graphics: League 1, 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).
Accrington created the most chances in the division by a comfortable margin this season but left themselves fairly open in defence and had to settle for a mid-table finish. While promoted Rotherham were the most dominant side overall, Wigan pipped them to top spot with a far less industrious attack.
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:
Champions Wigan created a fairly average number of chances this season but were the most clinical team in front of goal; MK Dons‘ promotion push followed a similar pattern. Only relegated Gillingham were more wasteful with their opportunities than shot-happy Accrington, with Burton also undermined by some unfortunate finishing.
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:
Rotherham operated the best defence in the division by some distance, although Plymouth exhibited a similar degree of resistance that almost saw them reach the play-offs. It wasn’t just wasteful finishing that was an issue at Accrington this term: they also absorbed the fewest shots per goal conceded.
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 looks like Rotherham were the best performers in the division and therefore worthy of another promotion to the second tier. While the identities of three of the bottom four teams are not surprising based on this data, Wimbledon appear unfortunate to have been relegated.