Thank you for your thoughts and opinions on the matter, however, the players all know what is expected of them to secure playing time and I can assure you that . . .
. . . your son and I have talked about what he can do to get more innings (if the player and I have actually discussed it)
. . . I would be more than happy to speak with your son about it, if and when he comes to me about it (if the player hasn't already asked).
It's been my experience, that in these situations, I find it best if the parent discuss the expectations and possible changes with their son, as the player already knows, or should know, what he needs to do to receive more playing time.
I will however, tell him of your concern at next our practice and see if he's willing or able to make the necessary changes. I thank you for your thoughts; is there anything else that I can help you with?"