
Originally Posted by
Cephius
Really, defense is where Sabermetrics simply fails next to a good baseball eye who watches the plays. Things like zone rating and defensive win shares are decent for giving an overall idea at how good a player is at his position, but there are simply too many factors that are unquantifiable.
For example, defensive stats don't take positioning into account, so if Chawlie tells Polanco to hug the line and he misses a ball to his left, his stats take a hit when in reality he was positioned poorly by his manager. Tex's UZR is well below average but anyone watches him knows he's an elite fielder. There's no way to calculate the relative difficulty of a defensive play, the jump an outfielder gets, a 1B who saves an error with his glove... etc.