I say let him come back the same time as Perkins. Why even come back now?
Well, I'll assume Jeff mean Jermaine O'Neal, but I'll take a pass too.
However, I think the advantage to JO coming back now is that it helps keep the whole team rested. Even on Semih's best nights, Doc needs to overplay the Big Three while he's out there to make up for his inabilities.
Having JO back will hopefully improve the team enough that Doc can give the Big Three a few extra minutes of rest per game without having to worry about always having them out there to make up for others' inabilities.