I've always believe that you judge an athlete's greatness based on his rivals. The great ones always had a great rival/rivals that brought the best out of them. Martina had Chris. Borg had Connors/Mac. Mac had a bunch (Borg, Connors, Lendl, etc..). Sampras had Agassi, though this was rather lopsided. He spanked Agassi on fast courts and got spanked in the 1st/2nd round on a slower surface before reaching Agassi. I don't see any great rivals for Fed. Nadal is great on clay but can he push Fed on any other surface? Time will tell, but I have my doubts. Hewitt gets beaten badly on a regular basis. His game does not match up well. Roddick, I've never seen a top player lose so badly, so consistently to fellow top players. He just doesn't have the brains or fight to push Fed. Safin has as much game as any but does not have the desire to dominate on a regular basis. I don't think we will ever see his best or can truly guage his greatness without a great rival.