Anyone up for a downgrade?

So the Celts are apparently gonna trade Nate Robinson and Kendrick Perkins for Jeff Green and Nenad Krstic. Now I'm not one to comment on sports normally, but I just don't see any sense in making a move like this. I mean we gain a pretty solid forward in Jeff Green, but Nenad Krstic? Really? That's downgrading our center and aside from Perkins, we really don't have anyone solid to fill that spot. Shaq isn't as good in his old age and Big Baby is good coming off the bench, but that's where he should stay. Not too bummed about Robinson but it's gonna be sad to see Perk go. I hope Ainge knows what he's doing.