By my reckoning, you have made a mistake by allowing him to go under 80% with 2 games remaining in the RS. Clearly, you must start him to get him to finish 21 of 26! CT minutes likely count, but CT starts probably don't. NT anything does not matter.
However, he's +5 on WE. I would guess that finishing him with 21 starts in the RS and playing significant minutes in the CT (over any promised made) and your nearly 100% safe...even if you sat him the whole way through the NT!