Coming to grips with today's forehand
Some coaches, including the Frenchman Patrice Hagelauer, no longer describe it as hitting the ball; they describe it as slapping the ball. "Nadal does it all the time," said Hagelauer, a former national technical director in Britain and France. "The extension of the wrist plus this internal rotation of the arm generates great racket speed and it can do so without a very long swing. It's a great innovation."
What makes Federer unusual and devastating is that he makes use of the windshield wiper effect on his forehand with a much more neutral grip: more modified eastern, or classical, than semi-western.
"If you look at people whose grips are similar to Roger, like Andre Agassi or even Pete Sampras, they tend to finish with the racket more on edge more of the time, and they tend to turn it over radically less," Yandell said. "What Roger has done is really synthesize the advantages of the classical and extreme style."
His grip allows him, like Agassi, to play closer to the baseline than most and take the ball early. But his hand and forearm rotation and open stance allow him, according to Yandell, to generate spin averaging 2,500 total revolutions per minute on his forehand versus 1,800 rpms for the likes of Agassi and the now- retired Sampras when they were filmed.
"Roger's hitting it as hard but with thirty to forty percent more topspin," Yandell said. "That allows him to find places on the court that nobody since John McEnroe has found, in my opinion."
"Nobody else looks like Roger," he added. "I don't think anybody else has the natural ability to play with the conservative grip and be able to rotate their hands and bodies that way, at least not yet."
To give an idea of what Nadal's competition is up against, Yandell's measurements show an average spin value on the Spaniard's forehand of 3,200 rpms with a maximum reading of close to 5,000.
"That's equal to or slightly higher than the spin values on the second serve of Pete Sampras," he said. "It's incredible."
Nadal often generates that spin with the reverse forehand: a buggy whip of a shot that was popularized on the run by Sampras in the 1990s but is now being employed in more static positions on court.
"Nadal takes it to another level," McEnroe said. "That's probably why his bicep is so huge, even though he says he doesn't do a lot of weights."
Robert Lansdorp, a coach based in California, has taught the reverse forehand for more than a decade, after picking it up from Sampras, and it is no coincidence that two of his most successful pupils - Lindsay Davenport and Maria Sharapova - make frequent use of it.
In theory, the shot allows the player to make more out of a vulnerable situation, trading horizontal swing speed for vertical swing speed and generating more spin and angle - and perhaps more pace - in the process than a shot executed by swinging across the body from an extended position.
Sharapova sometimes uses the reverse forehand from a position of strength in midcourt. She also uses it when she feels rushed, or has to deal with a low ball, because it allows her to generate racket speed in an uncomfortable position. But some wonder whether she and other aficionados are taking a good thing too far.
"I don't necessarily think it's the best shot when you're stable," McEnroe said.
Still, it bears remembering that today's doubter is tomorrow's tennis convert.
"When I was 15, my coach told me I was crazy to hit an open-stance forehand; he told me to get off the court," said the former top 10 player Brad Gilbert. "What I promise is that when I'm 60, if the players are doing something that looks crazy and it's working, I'm not going to say they shouldn't. I'm going to say, 'I'm behind the times.'"