The slider even when thrown correctly puts the most strain on the arm than any other pitch. He doesnt need it Q. With his good fb and a change and the curve that he is developing he will have all he needs in his arsenal for now. I would work on changing speeds on the fb as well. Put your energy in location location location. Mechanics Mechanics Mechanics. Everything else will fall into place. With his great work ethic and ability he will be fine. He is already one of the best 08 pitchers in the state. Keep doing what you have been doing. No need to take a risk of injury to a fine healthy arm.