There is probably required paperwork, physical, blood tests, and other things that have to be done to be eligible to tryout. Without those he will be told no at most D1's I know of. It is not a true open tryout. He needs to go by the Baseball office immediately. When my son attempted to walk-on it cost us $200 and 2 weeks for all the medical stuff that had to be done and then they cancelled them the day of.