The Sox should start bringing him in in the 7th inning and then the 6th, so he can be building his endurance.
As a starter you have room to make a mistake here and there, all starters get better as the game goes on, usually the 1st and sometimes the 2nd innings are usually the worst.
They need to pitch him longer, not give up on him.
Eventually, by the end of the 1st week in September, he should be starting....
If they have any hope for the playoffs, it will be as a Starter.
Jimbo