After winning the French Open, Rafael Nadal during his post match interview gave everyone that was watching what title he was zeroed in on after reclaiming his King of the Clay title. He told Johnny Mac that he wanted to add the US Open to his trophy case. What had hindered Nadal in the past was not that he was a poor hard court player, but after playing front loaded schedule his body simply could not withstand the hard courts. He was broken by the time September came around. Anyone that plays tennis knows that hard courts can be grueling on your body. Add that with Nadal's physically demanding style of play meant he was running on empty.
This year though he really cut down on the number of tournaments knowing that if he came in healthy he'd have a great shot. What you've seen is a fresh Nadal with an improved serve that gets him free points that he's never had before. Nadal has been a great player, but always lacked a serve that was a weapon, which only compounded the number of balls he would have to hit. Now, he's getting more free points, which keeps him fresher, longer. Not that conditioning has ever been an issue for Rafa, but I'll take an ace/service winner over a 15 stroke rally any day. I don't care who he's playing (props to Djokovic for a great semi-final), but he's winning this match. He'll have a career grand slam and a chance to have all 4 titles at the same time if he can win the Aussie Open-something Federer has yet to do.