I think people are being too critical of Krstic and heaping on too much praise on Perkins. This isn't simply a one for one trade. There are many ramifications to this trade that go beyond the stats that Perkins and Krstic put up. There are many things to consider.
First, in terms of offense, Krstic is a better fit for this team than Perkins. This should be evident by the past few games as it is irrefutably clear that Krstic fills a hole on offense that Perkins could not. Krstic spreads the floor and opens things up for Rondo (whether he takes advantage of that or not is another story). He can shoot, he crashes the offensive boards and he has very good hands in the post. Inside scoring is something we lack when Perkins is on the floor and this is something to consider.
Secondly, the injury bug has hit us hard this year. Perkins is out for an extended period of time and whether people like it or not Perkins is very injure prone. His shoulders and knees are recurring issues that have and will continue to hurt this team. Krstic is much healthier and longevity and reliability are important factors for any team, let alone one thats had the issues we have.
Thirdly, people are over-emphasizing defense. Take a look at the rankings. We're second in points allowed per game. Whether we allow points to be scored against us from the perimeter or post players is irrelevent. You need to take the whole picture into consideration. We're perhaps the best defensive team in the league (along with the Bulls). This tells me that defense is a product of the strategies and schemes employed by the coaches, not simply the impacts of one player. Which, consequently, leads me to another sub-point that Perkins has not played much this year at all and we're still top in the rankings. Krstic will be reasonably effective on defense and that's all thats needed.
Finally, I just need to state that we got Jeff Green in this trade who is central to the future of this team and also who proides a necessary role. The bench is stronger now and this is also an important consideration.
As to rebounding, I cannot argue that Krsic makes us better. I concede that he is an ineffective Center for this purpose. However, this team does no stress rebounding as a whole anyways. We are one of the worst rebounding teams in the league with or without Perkins so whats the difference? People complain about size in the playoffs and how that lost us the series. I disagree. We choked. Plain and simple. We had a lead in Game 7 and blew it. Not due to rebounding but due to mental lapses and an inability to score when it was needed the most. In the end, rebounding is correlated with winning games but it does not imply causation. Want to know the best rebounding team in the league? It's the Minnesota Timberwolves and they're wonderfully terrible. Rebounding is only important if you can translate it into a better defensive efficiency or to more points scored. A good offense and a good defense are what makes a team win. If you score more points than you allow: you win. Plain and simple. The Celtics are one of the best defensive teams in the league and they lead the league is assists per game. To me these indicate that we have little to worry about. Though some people raise valid points I think that most are still thinking with their hearts and not with their heads. In the end Krstic, Green, Murphy, Pavlovic, and Arroyo are stonger than Perkins, Robinson, Erden, Daniels, and Harangody (especially when you conisider the health of these players and the aforementioned points). Good day.