Today's stat post

Defense. UZR. Go read.

What does it stand for?: Ultimate Zone Rating. Devised by baseball statistician Mitchel Lichtman, it's based on Zone Rating, a defensive stat kept by STATS, Inc. that measures a fielder's success at getting to balls determined to be in his "zone" of the playing field.

How to calculate UZR: The baseball field is divided into 78 zones, 64 of which are used in UZR calculation. (As Lichtman explains, infield line drives, infield pop flies, and outfield foul balls are ignored. Pitchers and catchers are not included.)

Here's what is calculated for each zone: the out rate and the percentage of balls in that zone that turn into outs. The league average out rate is then subtracted from the player's out rate — if this number is negative, it means the player is worse than league average. If it's positive, it means he's better than league average.

That rate is then multiplied by the number of balls that hit in that player's zone. This yields a Zone Rating. To obtain the run value, it's multiplied by the Zone Ratings that are calculated for each zone the fielder covers, and then summed. This sum is a simple, unadjusted UZR. It is then further adjusted for park factors, batted ball speed, which side of the plate the batter was hitting from, the pitcher's groundball/flyball ratio and the number of baserunners and o....

Oh, just go read the post.