While Roy's psychological theory about the loss of Perk may or may not be true, I think the more likely psychological problem is that we're now playing our second straight season under this strange paradox:
If you so much as break a toenail, you must sit out a minimum of two weeks. However, if you're playing, despite your age, we'll run you into the ground (see Ray Allen playing 41 minutes against the Spurs).
First, I think this philosophy has worn down the likes of Ray Allen and Paul Pierce. Second, I think when the players get worn down, they start to ask themselves just how much they should push themselves if the organization doesn't really put that much stock int he regular season. And I'm not overexaggerating here. How many times this year has Doc or Danny told us a player is out, but if it were the playoffs, he would play?
Just look at Jermaine O'Neal. Look how pleasantly surprised all of us were about his physical abilities. Why? Because he likely could've played weeks ago; however, we decided that what was really important was that he was 100% come playoff time and that any help he could've given us winning the past 10+ games really wasn't as important as that.
And when that's the prevailing philosophy of the ball club, can we really fault our Big Three for settling for jump shots and conserving energy for the playoffs?