Scatter graphics: National League, 2 Mar 2016
Here are updated scatter graphics for the National League, which compare the attacking and defensive performance of each club. These are explained here if you haven’t seen them before and the previous instalment is 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).
Grimsby remain the division’s most dominant side, having taken more shots than anyone except Woking and allowing fewer than everyone else; marginally fewer than fellow promotion-chasers Eastleigh.
Woking may create plenty of chances but only two clubs – Welling and Altrincham – have allowed more. At the opposite end of the spectrum, Eastleigh and fellow play-off hopefuls Braintree allow few shots but don’t take that many themselves.
Gateshead are comfortably inside the top half despite taking fewer shots than anyone else – this will become less mysterious in the next graphic.
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 mentioned Gateshead above as doing well despite taking fewer shots than anyone else, and we can see here that they are the most clinical finishers in the division.
While it’s no surprise to see the likes of Grimsby and Cheltenham among the sharpest finishers at the bottom of the graphic, it’s interesting to see newly-promoted Bromley netting with similar precision.
Welling look cut adrift in the top left, having taken few shots while also being the most wasteful finishers by quite some distance: it’s taken them roughly twice as many attempts to score each goal on average than the division’s most clinical sides.
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:
Leaders Cheltenham stand out here: they have been impressively resilient at the back, soaking up almost five more shots for each goal conceded than the average club.
Meanwhile, despite allowing even fewer shots than the Robins, Eastleigh have conceded very readily from those their opponents are able to take: it’s taken less than half as many attempts to breach them on average.
Alongside promotion-chasing Braintree and Forest Green it’s encouraging to see that newly-promoted Boreham Wood are among the division’s most resilient defences.
While Altrincham have allowed the most shots by far, they’ve been slightly better than average at keeping them out. The likes of Torquay and Halifax have been far more vulnerable from a smaller (although still above average) number of shots faced.
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:
Grimsby remain ensconced in the bottom right corner: when shots are corrected for quality they stand out as the division’s best all-round performers this season.
In the top right we find Bromley, who we’ve seen are impressive going forward but at the expense of defensive solidity, which is nonetheless entertaining for the neutral.
Altrincham are currently sitting just outside the relegation zone and the sheer volume of chances they allow – far more than anyone else – is a real concern. At almost two goals’ worth of shots per game, this is more than double what Wrexham, Tranmere and Grimsby have permitted.