'It is given that over a large enough sample, all defenders field virtually the same number and type of batted balls to their zone.' I don't think it's a given at all, and if you look at innings played, BIZ and Plays on Fangraphs, it shows that isn't true. In any event, the amount of Balls in Zone (BIZ) is used to calculate their RZR, along with the amount plays made in the zone. The zone for shortstop is set for everyone and the amount of balls that go into that zone is used in the calculation along with the amount of the balls in the zone the player converted to outs. ' Likewise, we can also assume defenders will have the same opportunities to field balls outside their zone.'' I don't see how this could be assumed either. In any event, RZR measures the range. OOZ measure the amount of balls fielded outside of the position's set range. ZR used to have RZR and OOZ combined, but they felt it wasn't giving us accurate info, so it divided the two. You need to take a look at both to get a good view on the overall skill of the defender, but range is RZR. Your 'given' and assumption seems to suggest you wanna discount RZR all together as all the numbers needed to calculate it will equal out if you project out far enough. Seems you just want to use OOZ as the measure of range, which is cool if that's what you wanna do...but that's not the stat for normal range of the player. And if you wanna just go by what you see, I didn't see exceptional range by any means. He came in on balls well, but his side to side was nothing special