Baseball's sabermatricians often talk about range factor, zone fielding, and runs saved when calculating defensive statistics. I'm not sure if any of it actually translates into wins on the field for a team, but if it does matter, it doesn't seem like the Yankees made the right decision about moving Brett Gardner to centerfield and shifting Curtis Granderson to left field this season.
While it's somewhat of moot point being that Granderson has missed the first month of the season due to a broken arm and Gardner has had to play centerfield, since the Yanks have no one else who could really do it everyday, taking a look at Gardner's defensive stats seem to show that he hasn't made much of a difference.
In 19 games and 172 innings to date Gardner has been minus 6 in runs above or below average that a fielder is worth based on the number of plays made. Over the course of a 162 game season that means he would cost the Yankees 40 runs. Hardly the type of stat that you would want from your regular centerfielder. His current range factor is 2.30, only slightly above the league average of 2.26.
While it's obvious Gardner's speed allows him to cover a lot of ground and get to balls that other fielders would not, at the moment the statistics don't support the idea that he is an outstanding defensive centerfielder. On the other hand, it could mean that sabermetrics don't mean all that much. As long as the fielder doesn't make any obvious errors on fly balls or throws, perhaps the .04 percentage difference in range factor isn't going to translate into a championship for a baseball team.