Friday, December 30, 2016

On Rangers' "Non-Scoring" Midfielders

Craig Fowler recently published a piece in the Scotsman focusing on the goal scoring woes of Rangers' midfielders Barrie McKay, Jason Holt, Josh Windass, and James Tavernier.

Indeed, these four have combined for only 2 goals in 59 league games this season.

However, anybody with a cursory understanding of football analytics will tell you that goals per game, the stat Fowler focuses on, is a pretty useless measure of future performance. It is better to use shots, shots on target, or, the currently accepted gold standard, expected goals.

Thankfully, Matt Rhein over at The Backpass Rule has been compiling these stats, and more, for SPFL Premiership players this season.

Here are the totals for Rangers' "non-scoring" midfielders so far this season.

Minutes: 4756
Shots: 70
Shots on Target: 24
Expected Goals: 8.27
Actual Goals: 2

So McKay and company have scored ~6 goals fewer than expected based on the quantity and quality of chances they've created. To put this under-performance into context, consider the fact that Rangers have drawn six times so far this season.

Typically we would expect the difference between actual and expected goals to converge to zero over time as the number of shot attempts increases. 70 shots is not a large sample considering how long it takes for conversion rates to stabilize.

Don't be surprised if McKay and company start scoring more goals as the season progresses.

So Fowler was correct to point out that Rangers attacking midfielders are under-performing this season. However, he was wrong to assume that they would continue to do so. They might, but that would be unlikely.

A more relevant question is whether or not McKay and company are creating enough chances. For the sake of comparison, here are the same stats as above, but for Celtic's top 4 most-used attacking midfielders (Sinclair, Armstrong, Rogic, and Forrest).

Minutes: 3856
Shots: 140
Shots on Target: 55
Expected Goals: 15.95
Actual Goals: 26

Ignoring the over-performance in actual goals (which is not likely to continue), Celtic are getting twice as much productivity out of their attacking midfielders as Rangers.

No matter the outcome of this weekend's derby at Ibrox, this gap should be a major concern to Rangers fans.