Scatter graphics: League 1, 5 Oct 2019

Now that a meaningful number of matches have been played this season, another update to the scatter graphics seems justified. 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.

Shot dominance

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).

The situation at Bolton means that most of the charts for League 1 will be very skewed and very red, although they’ll hopefully they’ll improve as the season unfolds. Here we can see that the Trotters have allowed roughly three shots against them for every one they’ve taken. Wycombe‘s attacking output is second only to Doncaster‘s and suggests that their impressive start is no fluke, while Blackpool‘s own high placing is a bit more surprising based on this evidence.

Attacking effectiveness

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:

I’ve had to make this chart taller to fit Bolton in without rendering the rest of it illegible: their dismal return of two goals from 61 attempts surely has to improve. The Trotters’ position is obscuring some worryingly poor finishing at Shrewsbury for the second season running while Doncaster‘s own wasteful shooting helps to explain how they can be out-creating the rest of the division but sitting outside the play-off places.

Defensive effectiveness

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:

Ipswich‘s defence has been performing heroics so far this season, repelling over 20 shots for each goal conceded. Burton have also benefited from resilience at the back, particularly as only two clubs have allowed opponents to shoot more regularly. Southend meanwhile are having a pretty miserable time of it, with the most porous back line in the division.

Expected goals

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, Bolton are allowing their opponents over five times the quality of opportunities that they’re carving out for themselves, which is an improvement on the early part of the season but still ridiculous. Ipswich appear to be the best performers overall, but Fleetwood are running them close. Wycombe have been the most impressive attackers but are potentially vulnerable in defence.