Scatter graphics: League 2, 10 Feb 2021
Seeing as I last ran them in December it feels like enough time has passed to have another look at 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).
Carlisle‘s squad overhaul looks to have paid dividends as they stand alone as the division’s most dominant club in shot terms. The Cumbrians have taken 2.7 more shots per game than anyone else and allowed 1.4 fewer. Meanwhile Colchester‘s slide down the table is unsurprising given how many shots they’ve allowed (and how few they’ve carved out in return).
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:
A trio of clubs – Southend, Stevenage and Grimsby – have endured a horrible season in front of goal so far: creating little and struggling to convert the chances they do carve out. Carlisle may be outshooting the rest of the pack but they’ve also been fairly wasteful – leaders Cambridge are outscoring them despite taking almost five fewer shots per game. Exeter have also had no trouble making their opportunities count and are the division’s most clinical finishers.
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:
Salford‘s defence – or at least their goalkeeper – should be commended for being the division’s most resilient by far. It’s not clear whether they can keep soaking up so many chances successfully however. As in the attacking graph above, it looks like Cambridge are leading the division thanks to quality rather than quantity. At the opposite end of the table, Grimsby have allowed fewer attempts at their goal than all but four other clubs but have struggled to keep the ball out of their net.
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, Southend‘s attack looks worryingly adrift of the rest – they need a boost if they’re to fire their way out of relegation trouble. Carlisle are no longer the most dominant team (suggesting that a lot of the chances they create are of relatively low quality) but they’re still one of the best performers in the division along with Cheltenham and Forest Green.