Forman: The real problem with defensive stats

From SABR member Sean Forman at on September 8, 2014:

After reading Jeff Passan’s article about WAR and his view of its failings, I got a little hot under the collar and intemperate in my discussion of the issue on twitter.

The defensive metrics are constantly critiqued. I agree that there may be issues with the defensive stats, but my issues aren’t the ones brought up by the critics. I believe that the metrics do a decent job of measuring the percent of time a particular ball with a particular hang time has been caught in the past. All you need for that is a stopwatch and a way to mark the play’s location on the field. Sure there may be biases in this, but there are biases in who batters and pitchers face or even what umpire they appear against. So this isn’t the biggest issue with fielding stats.

It’s also true that fielding stats don’t correlate quite as strongly year to year as the batting stats do (see chart after break), but there is also a lot more variability in opportunity for fielders than for batters (and more variability in batting stats than people perceive). A batter is going to get 3-6 PA’s per game every game. The distribution of balls hit to fielders is much more random. But even this isn’t the big issue with fielding stats.

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Originally published: September 8, 2014. Last Updated: September 8, 2014.