These four players have unassailable talents, but each is lacking a certain element, which is holding them back from taking the next step. The corollary to this point has been a career of unfulfilled potential.
Roger Federer enters a tournament coming off a loss, while Justine Henin enters this week's Sony Ericsson Open as the world's No. 1 player. Joel Drucker writes it's business as usual for the top players on tour.