Have a look at Nadals to tourneys on US Hard Courts:
Cincinnati, OH, U.S.A.
Round Opponent Ranking Score
R64 Bye N/A W
R32 Taylor Dent (USA) 83 W 6-2, 7-5
R16 Julien Benneteau (FRA) 32 W 5-7, 7-6(6), 6-2
Q Marcos Baghdatis (CYP) 20 L 4-6, 6-4, 4-6
Dent was serving for the second in this one, then remembered who he is and his rank and decided against it. He lost because of 2924 errors. Nadal really was just there, didn't do anything to win this match but simple push the ball back. Then Benneteau?? ...hmm....that is an ugly win for Rafa, should have straight setted him with a blowout in second, instead, he was late on a lot of balls and hitting very short. Then Marcos gets him. This match Rafa actually played good, Baggy is just build for Hard Courts.
Toronto, Canada
Round Opponent Ranking Score
R64 Bye N/A W
R32 Stanislas Wawrinka (SUI) 24 W 7-6(12), 6-3
R16 Kevin Anderson (RSA) 87 W 6-2, 7-6(6)
Q Philipp Kohlschreiber (GER) 37 W 3-6, 6-3, 6-4
S Andy Murray (GBR) 4 L 3-6, 4-6
Tight against Wawrinka, that considers clay to be his best service. Then, big serving and one dimensional Anderson. Again tough win. Kohlschriber should not have won a set of him, but good comeback. Then Murray puts him to place.
The more I look at it, the more I think this year is not the one. He has little match time on hard courts this year, and each match was a battle so far. USO is best of five, so if he gives up a set in 2 early rounds....he will not last till SF or F. Will be just too tired to deal with the Big Boys of fast court.
Yes, he got to QF and SF but his draws were dreamy. Look at Fishes draw and who he had to beat to get to Finals.

Level 13 Edberg and counting...