Don't kid yourself. I can tell who is and isn't a good athlete from 50 yards away just by how they walk. Hard work matters, but its more about eliminating those with talent rather than allowing those without talent to compete favorably. Also, its a self reinforcing cycle. You have talent, you win, winning is fun, you work harder to win more, goto step 2.

PS The cutoff from HS to college sports is about as extreme as the jump to the pros...its less than 1% each time.