If Nadal can hold up he could be really great like the best ever. It's a toss up though he basically has missed close to 2 full seasons due to injuries already in his career. That knee could be problematic down the road. The thing that is impressive about Federer is that he is never injured. IMO it speaks volumes about the guy. He never retires like some of the other guys do Rafa and the Joker most notably. Roger is so fit he might be able to play into his late 30's if he still enjoys the game. Also Fed has twice as many majors sitting in the bag already. Rafa has to play catch up now. Still though if he can get a U.S. open title, a golden slam is a helluva acheivement. When all is said and done in another 7-10 years or so Sampras, Nadal and Federer will be the 3 best of all time and in a class of their own. It seems like the only thing stopping both Roger and Rafa from getting 20 slams each is each other and injuries.