Over the past few years, the Celtics have been hurt by a lack of continuity on the bench, with young players who couldn't play defense well enough to earn Doc's trust and Ainge projects. The Celtics, with their complicated offensive and defensive schemes, could use some stability on the bench with players who know the system instead of trying to integrate new players every off-season (and trade deadline and waiver period and buy-out season).
Avery Bradley is under contract and, unless someone offers him an insane contract or a new CBA changes things drastically, Jeff Green seems likely. Glen Davis seems to have played his way into a spot where Ainge will certainly look for a replacement, but perhaps settle on bringing back Big Baby for cheap. Who knows what will happen with Shaq. People here seem to like Delonte West, although his health is such a concern that maybe he should change his name to Delonte O'Neal. There's a current thread suggesting that Von Wafer should be brought back. Nenad Krstic has his flaws, but he's a guy who is worth more than the minimum salary and the Celtics need bigs. Troy Murphy is still a good rebounder and it might be worth a gamble, if he is willing to come back for cheap, to see if he can rediscover his shot. Carlos Arroyo would fill my desire to see the Celtics have a natural point guard on the bench behind Rondo so the offense doesn't stagnate when Rondo sits. Sasha Pavlovic is theoretically useful.
I wouldn't bring them all back and you need to dump some of them to make way for new draft picks, but the Celtics should bring back at least five of them so that there is some degree of continuity and chemistry on the bench with players who have somewhat of a head start in learning the team's system over free agents signed in the summer. I doubt Ainge will have a shot at bringing in markedly better players mid-season, and those players will be hampered by trying to fit into a new and more demanding environment. It seemed to take Marquis Daniels a year to find his place and get comfortable.