I was quite divided about this trade when it first happened. However, what's won me over is this simple fact: the Celtics were at their best when Kendrick Perkins WAS NOT on the floor.
In 2008, Doc routinely went with Posey to close out games. When it wasn't Posey, it was P.J. Brown (who could hit an 18 footer).
This year, it was the same thing. Even against teams like Orlando (who we supposedly need Kendrick for), Doc again went with the offense of Big Baby over the defense of Perk.
Is it because of free throw shooting? Partly. But if that was the sole case, Nate Robinson would've been closing games out for Rondo. It was because ultimately Perkins's defense didn't make up for his lack of offense: the Celtics were a better team with Big Baby than with him.
And that's what we saw with Shaq too. When you put another offender out there, it was just absolutely impossible to guard this team. And if Shaq's going to start games with the Big Four and BBD is going to close them, then what exactly is the enormous need for Kendrick?
And that's why I think Jeff Green could be huge. He's someone more offensively gifted than Posey, BBD, and (at this stage of his career) Shaq. How unguardable can this team be if he figures out how to play with the Big Four? We'd have four All Stars and another guy who soon could be.
Again, I'll miss Perk. But I think when you really examine who Doc has relied on over the years to get it done, Perk wasn't one of those guys.
I appreciate the effort to explain the thought process in detail, but that's a terrible post.
This season Perkins only came back from an injury a few weeks ago and has played only 10 games or so after being cleared out to play, half of them with a minutes limit. In any case,
if Doc was convinced that Baby was a better player than Perkins, wouldn't he play Glenn Davis more minutes than Perkins? But once he was cleared to play more than 30 mpg, Perkins logged more minutes than Davis in every game. How did you miss this? Anyway, saying that they were at their best when Perkins wasn't on the floor when the sample of him being on the floor is so small is misleading; implying Doc actions confirm that when he played Perkins starter minutes doesn't make any sense. Your closing line-up (and Perkins actually closed some games) is not always your best line-up. I remember Shaq close to his prime being out of the closing line-up in some games and he was very clearly the best player in his teams.
Then you mention the 07/08 season. For that one, we already have some large enough samples to draw conclusions. The best unit the Celtics that season with a minimum of 100 minutes played (with no minutes limit it was one with Eddie House, Tony Allen and Scott Pollard but no Garnett) included Perkins as did 3 of the top 4 units. The team's offense was 3.5 points per 100 possessions better floor and the team defense 2.5 points per 100 possessions better with Perkins on the floor, for a net gain of 6 points. On the other hand, with Posey the offense was 7.4 points per 100 poss. worse and the defense 3.8 points per 100 poss. worse with him on the floor, for a net loss of 11 points.
The Rondo/Ray/Pierce/Perkins/Garnett unit outscored their opponents by 19.47 points per 100 possessions while the same unit with Posey instead of Perkins outscored their opponents by 6.86 points per 100 possessions. Btw, that unit played less than 150 minutes in the entire season and was rarely used to finish a game. The fact that it was used as the closing unit in some playoff games, especially in the finals, leads people to remember it being used more than it actually was.
So, there doesn't seem to exist many evidence to backup your claim. In fact, all the evidence points out that the Celtics have been a better team with Perkins on the floor - even if sometimes, but far from always, Doc leaves him out of line-up that closes games.
Finally, you simply don't mention any season between 07/08 and this one, even though Perkins played 80% of his minutes as a Celtic during that period! You mention his first season as a full-time starter and the one where he played a dozen of games after coming back from a season ending surgery... and not the most important and relevant stretch of his career! I think we can agree it doesn't make any sense at all, no?
It's funny how people try to convince themselves that the trade was good by believing in the most extraordinary things when there are very good reasons why the trade was good and necessary. A little more nuanced than "he was never that good, I just understood that after the trade", "it was the injuries, I have faith Ainge must know something the OKC can't know" and "oh, we got the better player, future all-star", but still good reasons.