I understand your argument, but I think your word choice of "underachieved" isn't helping.
When it comes to a guy like Tiger, it's hard to call that guy an underachiever, especially when his work ethic is known and undeniable. The guy can barely walk and he's still out there trying...that's not an underachiever.
Underachieving, IMO (and I think what a lot of people think of when they hear the word) is when someone doesn't live up to to their potential, or work hard to maximize their potential...outside of being injured.
Plenty of things can de-rail a career, I don't think that means that individual is an underachiever. I don't think Griffey is an underachiever, I don't think Trout is, either. I just think they haven't had the careers they might have had if they were able to stay healthy.
When debating these things, it's helpful to have a definition of which to work with. So while I agree with you that guys like Tiger, Trout, Griffey and others haven't had the careers they were supposed to have, that doesn't mean they were underachievers. They just got de-railed...now some of that was their own doing, some of that is just the tolls of playing their sports.