Scatter graphics: National League, 6 Feb 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.

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).

NL Att Def 2016-02-06

Grimsby remain the division’s most dominant side, taking more shots than anyone except Woking and allowing fewer than everyone else; marginally fewer than Eastleigh.

Woking may create plenty of chances but only two clubs – Kidderminster and Altrincham – have allowed more. At the opposite end of the spectrum, fellow play-off chasers Braintree allow fewer shots than all but four clubs but only four have taken fewer themselves.

Gateshead are comfortably inside the top half despite taking fewer shots than anyone else – this will become less mysterious in the next graphic.

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:

NL Att 2016-02-06

I mentioned Gateshead above as doing well despite taking fewer shots than anyone else, and we can see here that they are among the most clinical finishers in the division.

While it’s no surprise to see Grimsby, Cheltenham and Eastleigh – all in the current top five – among the sharpest finishers at the bottom of the graphic, it’s interesting to see newly-promoted Bromley netting with similar precision.

The most wasteful finishers are another newly-promoted side: Boreham Wood have needed almost twice as many attempts to score each goal so far this season/

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:

NL Def 2016-02-06

Two sides stand out at the top: both Cheltenham and Braintree have been impressively resilient at the back, soaking up around four more shots for each goal conceded than the average club.

Despite allowing among the fewest shots, Eastleigh and Wrexham concede very readily from those their opponents are able to take.

While Altrincham have allowed the most shots by far, they’ve been slightly better than average at keeping them out. The likes of Bromley, Torquay and Halifax have been far more vulnerable from fewer shots faced.

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:
NL EG 2016-02-06

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.

Tranmere‘s recent surge into the promotion reckoning will not be a surprise to anyone who’s tracked their expected goals numbers: they’ve looked consistently strong in defence and their attacking performances have now improved to match.

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. The safety-first approach of Braintree in the bottom left has resulted in an average of just 1.9 goals in each of their matches, compared with the 3.5 witnessed in Bromley’s.