He can't hit lefties at all anymore. The Griffey/Diaz platoon is going to be about like moving Kelly Johnson back out to left field would have been. And while Johnson is a decent hitter for a 2B, as a LF, he's terrible. The Braves have about 3 or 4 guys who need to hit 7th, and nobody to put at the top of the order.
Griffey makes the roster better than it was yesterday, marginally, and so I guess it's a good move. But it's hard to believe that the "big outfield bat" that the Braves were talking about getting ended up being a 38 year old retread to platoon with Matt Diaz. This offseason has been a disaster.