OP-X: How to measure effectiveness in the box

Having already explained the basics regarding TSA’s shot location data (and how these principles can be used to make players score more goals), we will now take you one step further to understanding the details in our daily work with professional football players.

In this blog post we will explain the holy grail of shot location data in TSA. More accurate, we will explain how we calculate a player’s effectiveness in finishing in the box. We use a number, which we have named OP-X.

Before this, another term is crucial to understand. That is the term Goal Box Area. The Goal Box Area is marked with red on “The Pitch” below. Generally seen, 70 % of all goals get scored from The Goal Box Area in open play(see the blog post Shot Location Part 1 & Part 2, for the data that confirms this).

We calculate how many shots a player in average uses to score a goal in open play from The Goal Box Area. That is OP-X.OP-X is short for “Open Play in Goal Box”.

Open play is (with a few exceptions) defined as being more than 20 seconds after the latest set-piece-situation executed by the attacking team.

Why? It makes little sense to measure the overall shots per goal for a player, which is the general tendency in for example the sports media. It makes more sense to measure shots per goal (in open play) in the very area, where most goals actually get scored.

Furthermore, it is an advantage to use OP-X when working with a player on a daily basis. If a player aims to lower his OP-X, he will automatically try to take shots from The Goal Box Area, where most goals scored.

Summarizing, OP-X is a number, which indicates how many shots a specific player in average uses score a goal in open play from The Goal Box Area. Therefore, the lower OP-X, the better.

Robert Lewandowski, who recently was honored with the title as the best player in world, has 3,0 in OP-X. But the next generation is coming. Ansu Fati’s OP-X is 2,3.

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