This team never needed to gel before. They were always a dominant first half team until last season.
When you have a talented team on paper like the Celtics do, and they do, as a coach your first priority should be not to screw things up. Not to do so many unconventional things if it hasn't proved to work. I'm talking about giving the ball to Rondo all time, although it's been dialed back a bit lately and also KG's minutes. If every other team rests their best big man and defensive whiz early and sits him for long stretches, fine, but when every other team plays their starters for long stretches and you're mixing and matching from nearly the get-go, well, you're not going to be in rhythm and you're going to be at an disadvantage.
If Doc and Ainge feel Garnett is best playing 30 minutes a night, fine but rest him while the other team's starters are resting. That's all. The Celtics have a much better chance of surviving then. You can't play like Garnett is in foul trouble every game.