9:38AM Friday
March 8, 2013

I'm going to be honest with you: I have my misgivings about advanced defensive metrics-especially those that are publicly available to schmoes like you and me.- 1 - It's not that I think the methodology behind these stats is flawed or that the approach itself-is a-silly one-it's just that all these metrics seem a bit too reliant on two somewhat flimsy inputs.

First, there is the simple problem of sample size: it is unlikely that a single player will accrue enough defensive opportunities on different sorts of batted balls in a given year to give us a realistic impression of what his actual-skills are.- It's been said that you need three years of defensive data-I assume playing almost every day-to make up for this paucity.-

The second dubious input problem has to do with the data collection itself: the defensive metrics all rely on "stringers" who are actually at the game and tasked with classifying batted balls into categories.- For example, was that ball that Shelley Duncan gracefu