Pardon me for the harshness of this post but tell your son to either get over the disappointment and get to work or give him a hug and tell him you're proud of him for being a fine young man who is going to concentrate on academics and give up baseball. So one coach doesn't like him because he didn't hit the ball hard enough or far enough. Honestly, when I read your post and saw he only hit one out my first thought was this school isn't going to offer or at best drag it out hoping someone else steps up for them.
If he lets this one disappointment stop him then he probably didn't want it and / or wouldn't make it but it's something he can learn from. Get back to work, showcase this winter, knock on proverbial doors with his coaches help and have a great Senior year.
Good luck to him.