What are non-shots expected goals models for?

Back in February, I introduced a non-shots expected goals model at the OptaPro Analytics Forum, drawing on earlier work from a year ago. I talked about a simple version of the ball progression model that’s now one of several evaluators used by NYA. As the name suggests, the ball progression model gives teams credit for moving the ball based on the chances of scoring goals from the resulting positions. How should we interpret its results? The first generation of expected goals models attached a probability of scoring to each shot rather than to reaching specific positions on the field. These…
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The limits of expected goals models based on shots

When I try to understand a complex system like soccer, I usually find myself going through three stages of analysis. First I try to come up with a theory of the system that makes intuitive sense and reflects its actual dynamics, to the extent I can learn about them. Then I try to build a model based on this theory using rigorous statistical methods. Finally, I test the results from the model for their robustness, to make sure the whole exercise hasn’t led me to spurious or unwarranted conclusions. To my eye, the evaluation of expected goals models based on…
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2015 EPL top prospects redux

Recently I published a list of my top young prospects from the English Premier League’s 2014-15 season on the OptaPro blog. As I wrote there, the idea of the list was to cast a broad net, so that players of great potential would be identified as early as possible. This approach works well for clubs that can afford one or two false positives – supposed stars who turn out to be duds. But what about clubs that can’t afford to make a mistake? No model is absolutely foolproof, but I thought it would be interesting to look at a slightly…
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