So what went so drastically wrong?
Just about everything, as Josh Zavadil explained in a post on CelticsBlog. But the Celtics can and will make adjustments prior to Monday's Game 5.
Surely there are things that Boston will do differently in Game Five. Doc Rivers and his coaching staff have two whole days to review film and initiate the changes necessary to help the Celtics win, but Boston has to do a better job of running sets and not getting into what Doc Rivers likes to call "random offense." They have to establish Kevin Garnett quicker, and if he's being doubled in the post they have to find different ways to get him involved. If the Celtics decide to go to a smaller lineup, Rajon Rondo has to get to the basket and create looks for himself or open opportunities for others off of his penetration.
The Celtics could also use to take care of the ball (they committed 17 turnovers Friday) and hit the glass (Philadelphia won the rebounding battle 52-38).