There's some reporting that Ime is making some rotation changes to counter Warriors small lineups. Aside from the Nesmith possibility - which I agree is slim - I have a couple of additional thoughts.
I think Ime needs to bet on Rob. In games 2 through 5, the Celtics have been much better with Rob on than with Rob off. So I think Ime needs to approach this assuming that he will get 30 minutes from Rob, that the Celtics will "win" Rob's minutes, and that Ime needs to figure out how to win the minutes when Rob is on the bench.
I also think that part of the reason why the Celtics have been so much better in the Rob minutes is that Al Horford is just done. He's 35, this series isn;t a great matchup for him, and he's worn out from a long season and playoffs. I think his role needs to be reduced.
So, the Celtics need to plan with 4 types of lineups:
1. Rob and Al together as double bigs. If this works, play them together as much as possible.
2. Rob as the lone big.
3. Al as the lone big. But this lineup cannot see the floor against the Warrios small lineups.
4. Grant as the lone big. While Rob is out, if the Warriors go small, the Celtics need to match that with Grant at the 5, because the small Warriors eviscerate Al.