Defensive, particularly defensive rebounding. In the past 5 games, and probably before that as well, I have been appalled by the defensive rebounding. In the Bucks, Cavs and Wiz game I can distinctly remember a number of possessions down the stretch with the C's failed to grab easy boards and a few of these came after solid defensive possessions.
I am in particular thinking about a shot by Salmons and another by Hickson at the end of the shot clock. They had put up solid defensive possessions didn't get the rebound and then just failed to recover giving up an easy second chance. When you are struggling to play with energy for 48 you just cannot give up second chances like that.
Long rebounds on quick shots is fine but it is back breaking to grind out the possession force a bad shot and then give up the second chance. In each of the games (minus Indy) these things killed momentum and energy.
Lastly, this team was never a great offensive team. They play a slow and methodical half-court game. But when they run they can score in bunches and the fb starts with a rebound. If they aren't getting these rebounds they playing to their weakness on offense as well.
If they dominated the defensive glass they would be a better team. End of story.