i highly doubt a growth spirt will hit this late that will gain him 4-6 inches and 30-50 pounds, but i certainly could be wrong. i'd say start a high protein diet with lots of muscle and cardio work outs pronto! might also look into some supplements (creatine, protein shakes/mixes, etc...) to add some meat to him if he really has his heart set on playing guard.
~Andrew
