If you come back with numbers will it change your situation with this coach in this situation? No. The coach has seen your son play. He knows how hard he throws, how fast he is, etc. He has told your son that he thinks these other guys are better by playing those other guys more than him. A coach speaks with his line up card. Now if you come back with outstanding numbers for a LH Soph - posters can say "Yep that coach is crazy." "Your son is good enough based on those numbers." And what does that do for you?
The fact is there is only one thing for your son to do. Go out every day and work to change the coaches perception of him as a player. When he practices, practice harder and better than everyone else. When he gets opportunities take advantage of them. Instead of waiting for an opportunity, prepare for it. The coach doesn't think your son is good enough to play anymore than he already is right now. Change that. Change the perception of him as a player. Or validate it. I would choose change it.
And if he doesn't change the coaches perception, fine. At least he hasn't given in. At least he hasn't quit. At least he has the summer to continue to work towards those goals, He can work towards coming back next season and shoving in everyone's face when he is the better option.
You coming back and giving us numbers does not change one thing. It only gives people here an opportunity to say "Those numbers indicate he is an average Soph" "Thoes numbers indicate the coach is wrong." When the fact is not being there at practice and at games to evaluate the competition he is up against and his own ability means we have no freaking clue.
What I do know is that he is in control of one thing. How he approaches the situation. And you are in control of one thing. How you approach the situation. YOU support him. Encourage him. Point him the right direction. Stay positive and tell him to fight for what he wants. And he needs to do just that. Mid 70's with command for a soph LH can be Mid 70's with command for a LH Jr with a bad attitude. Or it can be upper 70's with command low 80's and shoving it with a fighters attitude. How hard is he willing to work for it? How determined are you to stay positive and be his best fan?
Don't get discouraged and worry yourself to death over this. Tell him to get in there and keep fighting. Tell him to talk with his arm, glove, bat and work ethic. Prove the coach wrong. As a coach I love to be proven wrong in these situations. There is nothing better than to see a young man overcome the line up card. It makes the team better. It makes a program better. Again, good luck.