Look no further than Hassaan Whiteside for proof. Here was a kid that had amazing size and athleticism in college - he average FIVE+ blocks a game in college. Then he got drafted and drifted through 5 years in the NBA, almost disappearing from the league because he didn't have the work ethic to make it. One day, the light goes on and suddenly he's through up a 14-12-3 a night.
Soooooooooo much about succeeding in the NBA is want and desire. Cauley-Stein is a physical specimen, but the NBA is filled with long players who are great athletes. If guys aren't willing to work hard and carve out a niche for themselves, then they won't be successful.