Scatter graphics: League 1, 2016/17

Now that the regular season is over here’s a final version of the scatter graphics, each of which 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).

Champions Sheffield United were the division’s most dominant side: only Bradford and Oxford created more chances and nobody allowed fewer.

Peterborough was the place to see goalmouth action this season: only the aforementioned three clubs out-shot them overall but they allowed their opponents plenty of opportunities in return.

With Chesterfield and Port Vale each occupying an extreme position in the upper left “red” quadrant it’s not surprising to see them relegated. However Coventry and Swindon seemed less terrible overall – we’ll see why they went down in the next chart.

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:

Scunthorpe‘s finishing was pretty clinical this season, with only six and a half attempts needed to score each goal on average. This was enough to give them the division’s second-highest goal tally (after the champions’) despite creating a relatively average number of chances.

Relegated Swindon actually took a similar number of shots overall but they were far more wasteful: only Oldham and fellow bottom four side Coventry needed more attempts to score on average. The reason for the Latics’ survival despite needing over twice as many shots to find the net than the Iron on average can be seen in the next chart.

Port Vale have been taking worryingly few shots this season, which is what prompted me to stick money on them finishing in the bottom half even when they were in the top six. However I didn’t expect the problem was unfixable enough to relegate them.

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:

Oldham are the uppermost team for the second graphic running: they soaked up over 13 shots for each goal conceded, which is four more than the average team. The result was that only three clubs conceded fewer goals and they live to fight another day.

As evidenced by their 4-3 defeat on the final day, Bristol Rovers‘ defending let them down at times this season: no club soaked up fewer shots for each goal conceded on average. Rochdale had similar problems, having allowed similarly few shots to promoted Bolton but conceding far more regularly.

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 Sheffield United lead the way at both ends of the pitch, with Millwall and Bradford the next most impressive overall: perhaps we’ll see those two in the play-off final?

Bolton‘s promotion looks to have been won in defence, where they looked far more impressive than up front. A similar observation can be made about Fleetwood – who ran them close in the race for a top two spot – while Scunthorpe secured their place in the play-offs despite some surprisingly average performances overall. The Iron’s lethal finishing looks to have made all the difference this season.