I'll be honest: I don't think the Celtics will repeat as champions.
There are three factors I can think of that will stop them. The first is their energy-oriented defense. The second is the loss of James Posey. And the third is the learning curve of the other NBA teams.
It is very, very tough to play with the kind of intensity and energy the celtics played with last season. And their three stars are all over thirty. I know Kevin Garnett is apparently Mr. Intensity but it only takes an injury to one of their three stars to really cut back on everyones intensity. Look for any small injury to Pierce, Garnett or Ray Allen to make them think twice about training so hard and playing so hard.
James Posey James Posey James Posey. How are they possibly going to replace him? He is like a rich man's Bruce Bowen: Bigger, stronger, and just as good at shooting threes and focused about defense. The recent NBA champions have had either Bruce Bowen, James Posey, Ben Wallace/Tayshaun Prince, or Kobe as a perimeter defender. I'm not too familiar about the championship lakers from five years ago but I'd assume they had some strong perimenter defenders.
Watching the games with James Posey he was always very strong at committing the "foul after the foul" to stop the continuation basket. He also was generally active on the perimeter and I good three point shooter. Some of his shots were only makeable because of his height, able to release the ball eight feet up and falling back slightly.
And lastly is the speed of learning for NBA coaches and players. Defensive schemes can be figured out. Tendencies set it. Players come back ready for the physicality, the intimidation.
I'm not saying the Celtics won't be good this year, but the Cavs, Pistons, Lakers, Hornets, and potentially Jazz will all be gunning for top status this year and will be gearing up for the Celtics. Thats what happens when teams win in sports. Everyone else gets ready to beat them specifically.