Tom Perrotta watched Rafa's destruction of Rochus and adds his thoughts on why Rafa's not the best on hard courts:
An opponent like Rochus, of course, doesn't tell us much about the form of the world No. 1. Nadal could win this match in straight sets on his a very bad night. But if you're looking for positive signs, well, there are many. Nadal is serving for the corners and hitting those corners. He's standing close to the baseline during (rather brief) rallies. He's stepping into his returns and moving forward whenever he gets the chance. The question, as always, is whether he'll be able to do that when the competition stiffens.
No matter how well he plays and how many titles he wins, Nadal still doesn't inspire as much confidence on hard courts as he does on clay and grass. This isn't surprising, but perhaps for different reasons, I suspect, than most observers suggest. The book on Nadal is that he often plays too defensively on hard courts (and hits the ball too short), and that he doesn't serve well enough. I don't think that's true these days, as his gold medal run at the Beijing Olympics showed. Nadal plays more aggressively each year, no matter the surface and his game is perfect for hard courts. It just happens to be more perfect for clay and grass. The chief reason? On cement, to my mind, Nadal's superior hand-eye coordination becomes less of an advantage. (Match update: Nadal spins, runs hard to the baseline, and loops a topspin lob winner. The lion roars again.)
How often do you see Nadal mishit the ball or hit an outright shank? Considering how hard he swings, and how much spin he applies with an extreme western grip, not too often. That's the case on clay and grass, too, where the bounces are unpredictable. In the rain, in the dark (the Wimbledon final), in the blinding sun, on clay, on grass--it doesn't matter. For everyone else, it does, or at least, it matters more than it does for Nadal. I can't help but think that his Uncle Toni, who made a point of teaching the young Nadal to deal with shoddy courts and conditions, has a lot to do with his nephew's impeccable timing, no matter what the ball does after it bounces. (Forehand winner down the line; Nadal to serve for the match.)
Hard courts, of course, give the truest bounces in the business. On hard surfaces, Nadal's supreme spin, so effective (and so unpredictable once it crashes into clay or a worn down patch of grass) becomes more predictable. His drop shot, which is underrated, becomes less of a weapon, too.
These are subtle difference, but important ones--differences that define wins and losses against opponents like Roger Federer, Novak Djokovic, and Andy Murray. It's not the whole story of Nadal's failure to win a major on a hard court, but it is part of it, and part that is too little discussed.