WIMBLEDON, England — A timeless tenet of tennis is this: Don't take your eye off the ball.
In the rousing five-set French Open semifinal between Novak Djokovic and Rafael Nadal last month, both players did just that, more than once.
Stretched wide on the run to their backhand side and forced to block the ball back with one hand instead of their customary two, Djokovic and Nadal occasionally eschewed the traditional slide, stop and sidestep back toward the center of the court. Instead, they continued their momentum and swiveled 360 degrees before sprinting back — losing sight of the ball, their opponent and, for a moment, the entire field of play.
"It's not the way to teach the kids," No. 1 Djokovic says. "But sometimes you've got to find your way back in play. I've won many points this way in emergency cases."
In an age of bigger, faster and stronger athletes wielding souped-up equipment, time is of the essence. And the sport's best movers are fighting back and pushing defense to new, improvisational heights.
"They are feeling the time pressure," says John Yandell, a Yale-trained instructor and digital videographer who has captured the move on film.
Like Agnieszka Radwanska's low-bending baseline half volley or Kim Clijsters and Roger Federer's lunging slice "squash shot" forehands (hers from a split position), the blind spin is the latest wrinkle in an era of defensive genius.
"They have ability to defend space that other generations were not," says Tennis Channel's Justin Gimelstob. "The rules have evolved as athleticism has evolved."
For now, only gifted athletes such as Djokovic, Nadal, Andy Murray and Gael Monfils do the swivel with any regularity — so new, in fact, even they haven't given it much thought.
"I'm really surprised to hear you bring this up," Djokovic says. "It's very interesting for me to talk about it because I know I can recall in several situations when I've done that."
For the moment, very few women do it, if any, at all. (Serena Williams says she has done it only a handful of times in her career.)
The movement is pure instinct. None practice it. They resort to it less on grass, where the footing (particularly this year at Wimbledon) is less predictable than hardcourts or clay.
Most can't recall when they first somehow figured out how to lunge, swivel and recover.
Second-ranked Murray, one of the best practitioners, believes he started doing it after he turned professional.
"I almost think it was once I got strong enough to start moving that way," he says.
He remembers the reaction from coaches.
"I was told not to do it," he says.
The no-look swivel is a calculated bargain. Players save an extra step by not placing an outer leg to stop and push back to the center of the court. Instead, they sacrifice court vision.
For spatial specialists, with their superior balance, speed, flexibility, footwork and peripheral vision, it's worth the risk.
"Athletes now find the most efficient way to move," explains Murray, who is seeking to become the first British man to win Wimbledon in 77 years. "The reason why we do it because it's the quickest way for us to get ourselves back into position on the court."
Some observers say the first player to turn completely around was American Andre Agassi when stretched wide on the return of serve. Murray, Djokovic and others also use it when returning.
Doing it while taking a step or two standing to receive is one thing. Sprinting, sliding, and pirouetting on the fly is taking it to a new level.
"I don't know how a mere mortal could do that and have the speed to recover," former top-5 player Brad Gilbert says.
Like the two-handed scissors-kick backhand innovated by Marcelo Rios, the lasso-like "cowboy" forehand epitomized by Nadal and the jumping overhead smash perfected by Pete Sampras, the game evolves.
Australia-based David Bailey, a footwork guru who has studied 10s of thousands of tennis clips in developing his own instructional methodology, describes it as crisis shot because the players can't hit with two hands from their outside leg in an open stance.
Technology helps. Rackets are lighter and with bigger sweet spots, which allows Murray and others to get their hand back quicker and control the ball while off-balance or falling away.
"It's a combination of a lot of little tiny things," Bailey says.
The biggest is positional "sixth sense," a skill that allows these uber-athletes to conjure up effective shotmaking off non-traditional stances.
"I don't know if you could teach that," he says, "but I love it because it's part of what makes them so good. They improvise."
Shoe tread technology, which has aided players' ability to slide on hardcourts, is another factor. The less interrupted motion, sometimes heading toward the back of the court, makes it easier for players to pivot rather than stop.
Strategy is another.
Pushing an opponent away from the middle of the court and sneaking into the net is a rare tactic in today's baseline-dominant game.
"I know that my opponent is on the baseline," Djokovic says, "or most likely I wouldn't do that."
Most coaches would probably say this: Don't try this at home.
"You need incredible leg strength and flexibility," says Patrick McEnroe, the general manager of the USTA's player development program.
McEnroe says that if his coaches can find a way to train kids to do it, however, "absolutely we will."
But tennis has it's own inevitable trickle-down culture.
"If it starts to be done more," says Nick Bollettieri, "people will start copying it."
Copycats beware: This move should come with a warning.