If your looking for someone to blame, blame human nature.
In what manner? If this was natural or inherent, wouldn't every team be going through something similar?
Its impossible for a team to get up for every single game, especially a smart team like this when they know nothing matters until the playoffs start.
Blake Griffin went at full speed for the first half of the season, now look at him, he burnt himself out.
Celtics are playing smart, why go full speed only to burn yourself out and have to struggle through the playoffs?
Eh... teams might not be able to get up for every game, but taking a month off when you're supposed to be integrating new guys into the system isn't the best idea.
Let me ask you this: how can we expect Green, Krstic, West, the O'Neals, and the other new guys to be ready to play full-speed in the Celtics system come playoff time, when those guys either haven't ever seen the Celtics system played correctly, or haven't seen it in months?
I just think it's a lot to ask of Green and Krstic to learn the rotations and sets, when nobody else on the team is doing what they're supposed to do. It's a recipe for failure.