I've already stated it. It's not perfect, but it's the best we've got, and it uses the best possible approach short of an electronic tracking system. To the detractors who get all wadded in the panties because one of their heros doesn't score well in a given year, I say heed the advice of the guy who created it. One year samples aren't enough to filter out all the noise inherent in attempting to measure fielding. This is like saying, don't measure how good someone is with an offensive stat over one month, which is accepted as common knowledge to most, including the "gamerzzz". Apply the same principle to something more complex like fielding, expand the window to a few seasons, etc..
Anyway, back to the game.