I would have him look at both strength conditioning and cardio workouts. For baseball strength conditioning is like all other sports you should have an overall program, but more concentration should be given to leg strength and arm strength. Use the leg press machine and squats for the legs and do curls, push ups, bench press and tricep work for his  arms. Legs are the key in baseball. They are your base. His cardio workout should concentrate on running sprints between 10 and 40 yards this will build up his quick muscle reflexes. Hope this helps. There are other exercises he can do, but this will give him a start.