So he's a second semester freshman, right? First year on his five year clock, and he hasn't played anywhere yet?
What happened? The obvious answer is the coach looked at his roster math different in February than he did in December.
The more important question is what can your son do now with the hand he has been dealt?
Step one is obvious: Spend the semester eating and working out like a horse. The weights are just as heavy in the NARP gym as in the varsity gym. Hit it hard. Sign up with a competent baseball-specific conditioning coach, even if it's off campus. Three months of hard work with good instruction and good nutrition can transform that long, skinny body.
Step two is also obvious: Work every contact he has from high school, travel, and college ball (including current head coach) to find a collegiate summer league to play this summer. He simply must get on a field against legit college competition as soon as possible if he wants to continue playing.
Step three is harder: Analyze baseball options for next year.
--Option One: If he stays where he is and this disappointment is repeated, his college baseball career will effectively be over. This option requires a lot of trust in a situation where none has been earned. I'd evaluate this option as "no scholly, no second chance" unless he's willing to remain at his current school as a non-varsity athlete.
--Option Two: Transfer to a JUCO with the goal of playing the 2016-2017 season and transferring to a 4-year school. The risks here are 1) not getting enough playing time to attract interest from a suitable four-year school. Most D1 baseball players who drop down to JUCO do not make it back to D1. It's a hard road, 2) ensuring he is academically eligible to play at a D1 right away as a 4-2-4 transfer; 3) not being able to map coursework taken at four different schools toward a degree he can earn in whatever number of school years you're willing to underwrite. This option can be perceived as assigning baseball a much higher priority than academics, so think it through carefully.
--Option Three: Transfer to a D2 or D3 at the end of this school year. The advantage is that he can play as a sophomore and have three years on one campus to restart something like a normal college baseball, academic, and social experience.
For all options, read the NCAA transfer guide carefully and maintain the best possible relationship with the coach as long as possible.
Best wishes,