If it were my son, I would advise him to request a meeting with the coach to say, "Message received. I realize I've had a bad attitude. I am sorry. I will work hard to improve. Please re-consider putting me on the fall team. If you don't, I will accept your decision and spend the fall working hard so I can show up at the spring tryouts ready to play with a better attitude and a stronger body. Please give me another chance."