Wednesday 21 November 2018

Non Shot Expected Goals Plus/Minus.

I last wrote about football's major problems when attempting to replicate the so called plus/minus stat from other, mainly US based sports here

In truth I only wrote it to work a spurious photo of Harry Nilsson into a football blog, but the objections raised were valid.

The main hurdle is the lack of goals, not a problem in sports where +/- exist (in mainly forms) such as basketball.

Five years on we may have a partial solution to lack of goals.

Goal attempts, expressed in shot based xG does improve the performance related sample size, but non shot expected goals models, applied to either individual actions or possessions, opens up a much richer source of data.

The problems of comparing changing lineups, the duration they are in opposition, the non shot xG differential and the venue, are purely technical and mathematical, as well as being difficult to compute on an industrial scale.

But non shot xG may have removed the final obstacle to creating credible +/- numbers for football, for which every defender and defensive midfielder should be hugely grateful.

If and when I finally data dump everything into a huge matrix & run off some figures, they'll appear here.

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