I believe the C's will get much better, just by improving their shot efficiency. It's difficult to be a defensive squad if your offense is so erratic:
FG:
Ray Allen 11/30
Tony Allen 10/29
Eddie House 3/18 (!)
Kendrick Perkins 5/13
Glen Davis 1/7
FT:
Rajon Rondo 12/24
Paul Pierce 14/22
So far, the defense has been up and down, but the offense has been really subpar. Only a great Pierce performance in the season opener has saved us from being 1-2 so far. The positive aspect is that sooner or later these shooting % have to go up, and therefore the whole team will solidify both ends of the floor