Crying over spilled milk now. You don't' have control over the coach and you made your best effort to discuss the issue. Now, have the conversation with your son and make sure he has that conversation with the coach. IOWs, have him talk to the coach and point out that he is not out of the woods yet, will walk a lot of hitters, will hard charge as best he can but needs the coach to understand that he can't stand out there and just throw. He can assure the coach that at some point this season, with hard work and good restraint on his pitching, he will be able to get back to where he once was or even better. However, that is a road to recover and he is not at the destination.