I highly doubt he'll be available tomorrow anyways. If he can't go and the C's sweep, then Finals it is.
Now if this goes 5, which it definitely could, maybe KP can come back and play limited minutes. But again, have we actually heard or seen footage of him actually practicing and doing up-tempo drills? You probably have to do some of that before getting on the court even for limited minutes.
Ultimately, I think the earliest KP can return is Game 6 of this series if it gets there, or Game 1 of the Finals. Yeah it might not be ideal in terms of "knocking off some rust", but Porzingis has been in the league a long time and also, once you get to the Finals there's only 2 weeks and 7 games maximum of basketball left. He needs to tough it out even if he's a little sore after Game 1.