There are lots of emotional reasons to hate the Perkins deal. And obviously it was driven in large part by financial reasons. But are there basketball reasons to defend this trade? I think there are, and though it's not the ideal scenario, given some of the Celtics' need I think it is driven by sound basketball sense.
It all, as the cliche goes, starts with the defense. What we learned through the first part of the season, surprisingly, is that the Celtics' defense is just as effective without Perkins as it is with him. The team's defensive rating was as high this year as last year. Further, as Rob Mahoney has shown with numbers, "Upon looking for meaningful statistical impact ..., it would seem that Perkins’ time on the court isn’t all that beneficial." The first part of the season taught Ainge that Perkins' defensive impact is, statistically speaking, negligible.
There are probably many reasons for this -- KG's return to form, Lawrence Frank's successful integration of Thibodeau's schemes, Shaq's pick&roll defense being less horrific than feared -- but the main one for Ainge's consideration is this: Big Baby Davis has developed into a fantastic pick&roll defender and overall very good defender. This also has been surprising. Couple this with his consistently hitting mid-range jumpers and his newfound ability to operate around the rim without getting his shot blocked every other time, and Davis has become an incredibly valuable player. The team doesn't lose anything defensively with him on the floor, and his offensive versatility and effectiveness make him the preferred crunchtime alternative to Perkins.
Of course lots of people are complaining that this makes us weaker against the Magic. There might be something to this -- though it should be noted that we still have Kristic, Shaq, and maybe Jermain to throw at Howard and that Davis has also been effective guarding him in the past -- but I think here is where Ainge is gambling: He doesn't think we will play the Magic in the playoffs this year. And I think he's right. The Heat are going to end up with the first seed, because they are healthy, have a weaker schedule, and have a bunch of home games, and will play the fourth-seeded Magic in the second round. And beat them.
The Celtics will have the second seed and will play New York or Philadelphia, then Chicago, then Miami. A team without Perkins actually matches up against all of those teams better than a team with Perkins: The Knicks are too small and quick, Perkins can't keep up with Noah, and we have interior advantages over the Heat that Perkins is unable to exploit. Perkins does not help and maybe even hinders us against the East juggernaut.
So what happens if the Celtics do make it through the East and has to play the Lakers? Well, things get a bit tougher then. But here's another gamble by Ainge: he thinks the Celtics won't meet the Lakers in the Finals this year. And by trading Perkins to the Thunder, he helped make it even more difficult for them to get through the West. It's almost devious, giving the Thunder the one piece they need to compete against the Lakers and the Spurs. Some people think that the acquisition of Perkins doesn't make the Thunder contenders. I disagree, and I think Ainge is gambling that it will.
So the Celtics sans Perkins are now primed to match up very well against the Spurs, the Mavericks, and the Thunder, better than they were before this trade. And even if the Celtics do meet the Lakers again, this year isn't last year: KG is rebounding at a much higher rate this year, Kristic is a decent interior defender, Shaq can rebound, etc. We are in much better shape with this roster than the game 7 roster that had only a fat, disinterested Sheed taller than 6'6".
It's a huge gamble by Ainge. But he was playing a difficult hand, because he had to get someone to take Daniels' spot. Considering his resources -- and considering the future of the team -- I think he made a good move. Will it work out? Well, as they say, we'll have to wait and see. But I think one thing is for certain: this was, in theory at least, a good basketball trade.