Scatter graphics: League 2, 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.
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 elephant in the room here is that Forest Green are currently top of the table despite taking the fewest shots of any team – the defensive chart below will shed a bit of light on this. Crawley have tended to be pretty quiet in attack during recent seasons, so to see them on the rampage like this is a pleasant surprise.
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 break out the extra-tall chart to accommodate the wasteful finishing of Stevenage and Walsall, although at least the Saddlers’ record in front of goal is gradually improving. We can see that Cheltenham have been the division’s most ruthless finishers, which has compensated for the low number of shots they’ve taken.
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:
So here’s how Forest Green can sit at the top of the table despite taking the fewest shots and allowing an above-average number in return: the ball just refuses to go into their net. I don’t expect them – or a similarly impressive Newport defence – to sustain this level, given how ridiculously out of the ordinary their numbers are.
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, Forest Green remain an enigma: it’s possible that they’re doing something too subtle for the model to pick up. Exeter look to have been the most impressive performers overall, with Bradford also looking capable of sustaining a promotion challenge. Walsall fans look destined to witness plenty of low-scoring matches at this rate.