In the glory days we had Johnny Mac, Jimmy Connors, Pete Sampras, and Andre. From absolute powerhouses in American tennis, to not having won a men's major since Roddick in 03', we luckily still have a legend in Serena Williams. However, at age 40,   are few successors that can carry on the dominance she has imposed on the game over the last 20 years. With the future of American tennis hanging on by a gut string, who is going to step up and take the place of the greats before them?