What it really comes down for me at this point is that the C's need 5 good bench players, and two that are fairly special. Aside from the Perk injury, I think not having a second special player at the 2/3 spot hurt us as Ray and Paul were out of steam by game's end.
If Sheed retires, I think Baby is now good enough to be that "special" bench player. Thus, I think we'd need someone at the 2/3 who Doc can feel confident to play major minutes in a meaningful playoff game. TA wasn't quite there and I'm not sure he'll ever be.
I think T-Mac is an interesting option. Even with Ray and Paul playing fewer minutes, he'd still only be asked to play 20-25 mpg, which is perfect for him at this point. He'd also take playmaking responsibilities from whoever backs up Rondo when Rondo's out.