Tough to be a quality rebounding team with this lineup.
No Rondo means that the Celtics will be out-rebounded across the perimeter. Ray is a weak rebounder, Daniels is a weak rebounder and Pierce is a below average rebounder most of the time. Nate is an average rebounder. Von Wafer is a poor rebounder.
Then add in Glen Davis and Semih Erden who have both been very poor on the glass this season (6 boards per 36 is pathetic for big men) and suddenly there is far too much pressure on Shaq (limited minutes wise) and Garnett to keep the C's competitive on the glass.
Anyways ... it's just an injury related problem. Once Rondo, Perk and Jermaine come back, the Celtics will be one of the best rebounding teams in the league. Rondo plus one of those big men makes the Celtics a quality rebounding team. All three make them a lethal rebounding team.
Edit: Sorry, Rondo played against the Raps. I missed the game. I thought he was still out. With Rondo, but without the two injured big men, the Celtics will likely get out-rebounded by a small margin on average.