There have been countless tennis rivalries between the top players of the sport. From Rod Laver and Ken Rosewall, to Andre Agassi and Pete Sampras. The current tennis rivalry between Roger Federer and Rafael Nadal is considered by many people to be the greatest tennis rivalry in tennis and modern sports. Eventually, it's going to pass, as all things. But there will be new players to take up the role. Who do you guys think will have the next great tennis rivalry?