Many college students, and athletes, change their major, so he doesn't need to be stressing out about it, but it's great that you're starting to ask these questions now.
Typical majors that can sometimes be difficult given the time commitment of being a college athlete are classes with required labs, or required group study sessions. Also, those can be more of a concern at smaller colleges where there may only be one or two sections of a lab compared to five or six sections from which to choose.
At one university where I worked, I recall a couple of athletes who quit their sport because of the conflict between practice and architecture labs (where they would construct models of their designs).
One other thing to consider for Division I programs. All Division I athletes must meet "percentage of degree" requirements starting with their junior year. This is commonly referred to as the "40/60/80" rule. They must have completed at least 40% of the specific course requirements for their chosen major by the start of their 3rd year of college, 60% by the start of their 4th year of college, and if still competing during 5th year, 80% of their course requirements.
This isn't an issue for the majority of Division I athletes who start at their college as a freshman, but can be a problem for transfer athletes when their credits won't transfer from one college to another.