Scatter graphics: League 1, 17 Sep 2019

As it’s been a good few years since I last gave them a polish, I’ve updated my scatter graphic templates for their first outing of the new season. 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.

While you can read more about them in the link above, here’s a quick summary of the main changes that have been made:

  • The stripes now actually mean something – before they were useful contours but now they’ve been anchored to the historical data for each division.
  • Where possible I’ve used a 16:9 aspect ratio so that the graphics fit a smartphone screen, only reverting to a retro 4:3 when the plot gets too cramped.
  • The style now matches my other graphics more closely.

It’s worth flagging up front that the relative difficulty of a club’s fixtures so far can have a significant impact on where they sit at this early stage of the season.

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. Hopefully they’ll improve as the season unfolds and we’ll gradually see a more normal picture develop. Wycombe appear to be the real deal based on early evidence, with Ipswich the other standout team, while a quiet Sunderland attack and permissive MK Dons defence are both causes for concern.

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:

Bolton finally scored a goal this weekend so that I could plot them on this chart, and the lack of chances they’ve created so far at least reduced the amount of skew. The Trotters’ position is obscuring some worryingly poor finishing at Shrewsbury for the second season running, while ruthless shot conversion at Peterborough and Sunderland is keeping both in 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:

Burton‘s defence has been performing heroics so far this season, repelling almost 20 shots for each goal conceded. Along with Lincoln and Shrewsbury, the Brewers have been asking a lot of their rearguards and generally getting away with it. 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 NINE TIMES the quality of opportunities that they’re carving out for themselves, which is frankly ridiculous. Again let’s hope that their dot drifts inwards as the season progresses. Ipswich appear to be the standout team at both ends of the pitch, with Gillingham and Wycombe both impressive in attack but potentially vulnerable in defence. Southend‘s change of manager makes a lot of sense based on the early evidence.