Inspiring is a good word for them. Sorry to hear about your friend's nephew, but it sounds like he is doing well, to make the team.
I know two men who each lost a leg (one from a mine in Vietnam, the other I'm not sure but I think was for medical reasons). The son of the Vietnam vet went on to become a prosthetics doctor because of his dad.
Neither of these guys played sports after their amputations, to my knowledge, although one has thrown out the first pitch at a Braves game or two. They are also two of the funniest guys I have ever met.