Wimbledon, England

Roger Federer is known for brilliance, for elegance, for wondrous shots that few players in history have been able to execute. If he wins Wimbledon this year, though, it will be because of his mastery of an oft-overlooked skill: Federer knows better than anyone how to bluff.

Roger Federer hits a forehand against Xavier Malisse. Panoramic/Zuma Press

Federer, who will play Novak Djokovic in Friday's semifinals, remains a Wimbledon contender only because he didn't panic when his back seized up in the fourth round against Xavier Malisse. As Federer struggled to move, especially to his right, and Malisse attempted to serve for the first set at 6-5, Federer needed a flurry of points, but he couldn't win them all with firepower. So he faked it.

The display that followed might be the most important sequence of shots at this year's Wimbledon, and it revealed Federerian qualities that are mostly ignored because in his prime, Federer rarely needed to rely on them: toughness. Deception. A willingness to dare his opponent to do something great.

"That's the beauty of our sport," Federer said in an interview Wednesday. "Even if you're not quite that confident, any game or shot can change momentum."

When Malisse served at 0-15, Federer camped out behind the baseline and hit forehands at half speed; almost all of them landed inside the service line. He poked and patted the ball as Malisse hit deeper, more powerful replies. On the 20th shot of the rally, Federer's footwork was so awkward that he had to lunge at a ball hit right to him. The 24-shot rally ended when Malisse missed a backhand.

Wimbledon Tracker

See how top players are performing at Wimbledon.

Two points later, at 15-40, Federer bluffed again with a perfect set play, the rare chip-and-charge. As Malisse tossed the ball for a second serve, Federer moved forward. He sliced a backhand but mishit it; the ball floated over the net into the middle of the court, waiting to be pummeled. Federer didn't care. He charged forward, dared Malisse to pass him and guessed (correctly) that Malisse would go down the line. Federer bounced to his left and hit a crosscourt backhand volley drop shot for a winner. In the ensuing tiebreaker, Federer rattled off six straight points to win 7-1.

"What I think I've been able to do well over the years is play with pain, play with problems, play in all sorts of conditions," Federer said. "And here I am, I made the semis. All of a sudden I'm feeling great about my chances."

That said, Federer has lost three straight matches to Djokovic and eight straight sets. They have never played at Wimbledon or on grass, and they are meeting at exactly the wrong time for Federer. He turns 31 next month; Djokovic turned 25 in May. Djokovic won Wimbledon last year and has played more aggressively here this year without making more errors. Federer, meanwhile, is moving backward—literally.

Since 2003, Federer has hit an increasing number of his shots at Wimbledon while standing behind the baseline, rather than inside it, according to data from the All England Club and Hawk-Eye Innovations, the company that provides technology for line-call reviews at three of the Grand Slams. (Hawk-Eye compiled data for all but four of Federer's career matches at Wimbledon through this year's quarterfinals; data weren't available for the others.)

In his first Wimbledon final, against Mark Philippoussis in 2003, Federer hit 66% of his shots from inside the baseline. Against Andy Roddick in 2009, that percentage dropped to 46%. Against Mikhail Youzhny in this year's quarterfinals, Federer dominated—the final score was 6-1, 6-2, 6-2—but he hit just 34% of his shots from inside the baseline.

Where Federer hit his shots from in the 2007 Wimbledon final. Hawk-Eye Innovations/AELTC

Where Federer hit his shots from in the 2012 round of 16. Hawk-Eye Innovations/AELTC

So far this tournament, he hasn't stepped inside the baseline for more than 36% of his shots in any match. From 2003 through 2006, when he won the title each year, Federer didn't hit fewer than 38% of his shots from inside the baseline in any of the 24 matches for which data is available. For all of those matches except one, he stood inside the baseline for at least 40% of his shots.

It isn't as if Federer isn't trying to step into the court. It's just becoming more difficult to get there.

"If he finishes points on, near, or inside the baseline, then generally things are going pretty well," said Paul Annacone, Federer's coach. "Against the best players, it's tougher to do."

Every year, there is a lot of talk about firmer ground beneath the grass at Wimbledon, truer bounces, slower tennis balls and new string technology that aids in hitting topspin.

Those are factors in Federer's Wimbledon retreat, but more important have been the improvements made by his competition—Djokovic, Rafael Nadal and Father Time. An aggressive game requires quickness and incredible confidence. If quickness declines, confidence will surely fade.

John McEnroe, the three-time Wimbledon singles champion and ESPN analyst, said he sees signs of aging when Federer approaches the net. He is also concerned about Federer's back. "It's one thing to move side to side when you're catching every ball waist high. It's another thing when you really have to get low," McEnroe said. "He may think that if he's not 100%, he has to stay back even more and trade ground strokes with Djokovic, which wouldn't seem to be a winning formula."

It wouldn't, unless, of course, Federer can win with guile. When he beat Djokovic in the French Open semifinals last year and ended Djokovic's 43-match winning streak, Federer played against type. He wasn't super-aggressive; instead, he was patient and used Djokovic's nerves against him. There is every chance he'll play against type Friday, if only because Federer can play more varieties of tennis than anyone else.

"He's going to have to play the best match he's played in a long time," McEnroe said. "But I always thought his best chance to win another Slam was here." Even if he has to bluff his way through it.

—Carl Bialik contributed to this article.