Sounds like the "Happy Gilmore" approach, lol.
Originally Posted by YankeesCatcher
This is a tough question.
This is about trust and fear. He needs to realize that there's nothing to fear if he trusts himself. The more you play catch with him, the more comfortable he'll get, progressing at his own speed/comfort level.
One thing you could do, is kinda like what YankeeCatcher mentioned. Stand very close to him with a real baseball, but have him take his mitt off. Get a coulple feet apart. Just toss the ball back and forth to eachother underhand; you could even tie his throwing hand behind his back. May not seem like much, but psychologically his comfort level will increase as the distance increases, and the more he sees the ball coming at him. In time, he will come to trust his barehand, and then wearing the glove will be no sweat.
"By common consent, Ruth was the hardest hitter of history; a fine fielder, if not a finished one; an inspired base runner, seeming to do the right thing without thinking. He had the most perfect co-ordination of any human animal I ever knew." - Hugh Fullerton, 1936 (Chicago sports writer, 1893-1930's)