Okay, that's a pretty highfalutin' comparison. There are on-the-ground aspects to consider as well. Practically speaking, all players are subject to conditioning, which is why it's usually important for them to establish winning traditions on various surfaces or at a variety of venues early in their careers. Nadal has accomplished this, on a large scale, with his Wimbledon performances and Masters shields.
Yet you could argue that Jet Boy has achieved that mainly on the strength of his fighting spirit and exuberant athleticism; in this interpretation, those have overrun the built-in controls and determinants. In theory, Nadal should not fare nearly as well as he has on those faster surfaces, but then the New York Giants weren't supposed to win the Super Bowl. One of the main reasons we love sports is because of their potential for sedition; we love to see theory ruined and expectations blown up. It tends to reinforce our hope that anything is possible in a way that poses no threat to our equally strong conviction and hope that it is not.
One critical aspect of Nadal's nature is that the non-clay tournaments in which he does well tend to be different from the clay events in which he shines only in the particulars having the most to do with technique and strategy - areas that are of lesser importance to Nadal's genius than others. That is, he does well at events that suit him, in some temperamentally rather than purely technical way.
Nadal's performance at Wimbledon last year was impressive to me because he kept his desire and spirits up despite the rain and gloom, not because he managed to cobb together a passable game to go with his mental and emotional strengths. The further Nadal gets from the warmth of the sun, the breezes that wash over a court, and the smell of freshly watered clay, the less well he does. Come the Paris Indoors, and he's a mess of conflicting signals - never a good thing for a predator. I think he responds to environment in as significant a way as he does to surface speed, and I know that's a pretty radical notion.
The most puzzling aspect of Rafa's resume is his relatively poor performances at the sunny, warm, colorful US Open. But in this, he's similar to many other players who are essentially provincial. The American major has proven to be a formidable stumbling block for many players from outside the U.S., and often for reasons obviously having nothing to do with the surface - and everything to do with the full menu of New York's famed distractions. In fact, Roger Federer's ability to overcome the habitual European fear of the American challenge is a particularly powerful testament to his versatility and underscores the degree that he has transcended whatever provincial urges once defined him. His most valuable asset in that regard has been his cool temperament; he took measure of the event and then tailored his approach and game to ensure a good fit.
TMF is a problem-solver; Rafa is a problem-attacker.
That suggestion may ring true for those of you who are familiar with all those studies about how little boys tend to try to break through walls while little girls are more likely to navigate around them. Nadal's greatest strength, as well has his most outstanding weakness, is his boyishness. This is a lingering condition that all but defines him to many of us. It is why so many people love him, and why disliking him has always seemed to me a little like disliking a kid brother. Rafa is the Little Engine that Could, never mind that he what he "could" do is blast a tennis ball through your forehead with such force that it would leave a volleyball-sized exit wound on the back of your skull.
But for all his bellicose instincts (does anyone else spank the ball as gleefully as Jet Boy?), he continues to engage us with incredible charm and insouciance. We all know how Uncle Toni insists that Rafa not get a swelled head - that Toni makes Rafa carry his own bags, and has him sweep the court after practice. We all know that the photo ops of Nadal tend to produce images of Rafa blowing out the candles on a birthday cake, surrounded by Spanish journalists in some press room, rather than shots of him with a dude all in black on one side, and a ranking fashionista on the other.