G Wallace is not even 31 years old yet. I know his contract sucks and his play is down lately, but he's not entirely terrible given the grand scheme of terrible NBA contracts.
He can fill a role and run with Avery, Rondo and Jeff for a couple years, and become a valuable expiring deal as others have already noted.
He's 31 this coming season. Certainly, not too old to have a bounce back year. 31!!