Scatter graphics: League 2, 4 Mar 2017
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).
Portsmouth remain the division’s most dominant team: nobody creates as many chances or allows fewer. Leaders Doncaster and play-off chasing Mansfield run them close at restricting opponents’ shots, while Blackpool and Accrington are the next most productive going forward.
Both Hartlepool and Crawley take far fewer shots than anyone else and allow among the most, although nobody comes close to Morecambe for the latter.
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:
We can see Accrington‘s problem this season: they may take the third most shots but nobody has been more wasteful at finishing. Profligacy also partly explains why Portsmouth aren’t leading the division despite all that lovely dominance.
Doncaster, who do lead the division, have been the most ruthless finishers and in-form Stevenage have also benefited from some clinical shot conversion despite creating a similarly 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:
Doncaster may be the division’s most clinical finishers but they have also soaked up fewer shots for each goal conceded than anyone else. However with only Portsmouth allowing fewer attempts at their goal this clearly isn’t a huge problem.
Luton‘s own promotion challenge – and to a lesser extent Plymouth‘s – are being powered by stubborn defences which have absorbed a lot more punishment for each goal conceded than the average team.
While Morecambe allow an obscene number of shots, only the aforementioned two clubs have faced more for each 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, Portsmouth‘s dominance looks even more pronounced, particularly in how well they restrict their opponents’ chances.
Interestingly Doncaster are now much further over to the right, suggesting a focus on shot selection i.e. they don’t take a high number of shots but they usually work the ball into good positions before shooting (which in turn explains why they are so clinical).
Luton‘s presence near the automatic promotion spots is no surprise given how similar their performances have been to the league leaders. The appearance of Stevenage in the top seven is perhaps trickier to explain given their relatively average showing – the clinical finishing we saw in the second graphic looks a likelier cause.