Here's the way i see it. the Celtics traded a banged up, recovering from knee surgery, going to leave at the end of the year center for a very good young player in Green and a desent back up big. The team had one of the best records in the league without Perkins playing so I don't see that as being the problem.
I do agree that having at least one of the O'neal's back should help, but the biggest problem is that for whatever reason the Celtics continue to go on long runs each game when they just can not score. I don't see how Perk fixes that, but the offense just goes out of whack. The ball movement stops, Ray doesn't get any touches, Rondo starts playing at half speed, KG can't hit a shot, West hasn't been the same player since he's been back, etc. Last night it also didn't help that they missed something like 5 of 8 free throws down the streach.
Blame the trade if you want, but I just don't see that as the problem. If all of a sudden the defense went south than maybe, but that's not even close to their biggest problem.