Not trying to squash anyone's arguments here, because I think fielding percentage is important, but using it to evaluate defense is probably something like using batting average to evaluate offense, in my opinion. It gives you a general idea. A player got a lot of hits and hits are good. It won't tell you if a player got off to a cold start, like how Mauer was hitting below .300 in June 2006 and then a month later was at .392 or how Dozier got off to such a cold start this season. Average won't tell you how much speed or power a guy has. It won't tell you a player's injury history. It won't tell you how old he is. Also, to summon Moneyball, it won't even tell you his OBP necessarily. Fielding percentage gets a chair at the table for sure, but that's about it. Not the head chair by any stretch. IMO.