Scream and Shout: an xClaim Model for Goalkeeper Cross Collection
/Ever since we built goals added (g+) oh so many years ago, I’ve largely been unhappy with how we’ve treated goalkeepers here at ASA. ASA, the masterful puppeteer in the shadows crafting the rise of Matt Turner and Djordje Petrovic to the Premier League, letting them down! And so, my fellow analytics practitioners, ask not what your goalkeeper can do for you, but what you can do for your goalkeeper.
ASA and the analytics community at large has gotten to a pretty good place with goalkeeper shotstopping, at least with event only data. You scale the saves they make by the quality of chances they face, you accept that’s a pretty noisy metric season to season, it tracks directly to goals, it’s sort of easy. We have done a somewhat less good job looking at how the other parts of being a goalkeeper impact the game. Goals added does an okay job, assigning the value of their sweeping to the situations they interrupt. But it’s an imperfect picture, the whole point of sweeping is that you are preventing a much more dangerous situation from occurring further down the road, but where you are now is not actually that dangerous on its own. The ball playing side is similar, goalkeepers are so far from goal that aside from long kicks up the field, virtually all the passing they do is meaningless in the eye of a possession value model.
Today, though, we start with cross claiming. If you take the entire MLS dataset we have at ASA, the most productive cross claiming season by g+ is about +0.5 g+ across the entire season. Half a goal. Intercepting a cross in the 6 yard box off the head of a striker itself is worth half a goal! It’s wrong, and I won’t stand for this goalkeeper cross claiming erasure #GKUnion.
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