Perhaps the surface and the setting matter in men's tennis, after all.
Roger Federer had lost six of seven matches to Novak Djokovic, most recently last month in a dispiriting, straight-set affair in the French Open semifinals.
But that was on red clay during a soggy second week in Paris when it was even tougher than usual to breach Djokovic's defenses.
Wimbledon was rainy, too, on Friday. But Centre Court now has a retractable roof and so Federer, with his suspect back and grand plans, was able to stay safe and dry on his favorite tennis court; able to shift the momentum of a great rivalry back his own way with a stirring and surprising 6-3, 3-6, 6-4, 6-3 victory in the semifinals.
"Obviously I'm ecstatic; I'm so happy," Federer said. "I played a great match today." It was the 27th match between Federer and Djokovic, but their first on grass.
"I think over all the surface made the match play differently and potentially in my favor," said Federer, who holds a 15-12 edge over all.
At age 30, Federer, the smooth-moving and enduring Swiss champion, is now just one victory away from tying William Renshaw and Pete Sampras with a seventh Wimbledon singles title. He is also only one win away from reclaiming No. 1 ranking.
To cross those thresholds, he will have to defeat the winner of Friday's second semifinal between Andy Murray of Britain and Jo-Wilfried Tsonga of France. Neither Murray nor Tsonga has won a Grand Slam singles title and neither has been in a Wimbledon singles final.
While Federer and Djokovic, the defending champion, played indoors Friday, Murray and Tsonga were set to begin their match outdoors after a break in the foul weather at Wimbledon.
Djokovic said he did not believe that playing indoors had given either player an advantage.
But playing indoors certainly seemed to help Federer on his serve. Djokovic, arguably the world's best returner, was able to break him just once. That came in the second set when Djokovic appeared to have taken control of the match after a quick start from Federer.
At that stage, Djokovic was winning a clear majority of the baseline rallies, holding serve effectively and making Federer lunge and scrape for volleys when he did manage to get to net.
But Federer was able turn the match in the third set despite failing to capitalise on opportunities on Djokovic's serve in the sixth game.
But with Djokovic serving at 4-5, the Serb retreated to hit an overhead and missed it long to give Federer two set points at 15-40. Djokovic saved the first but could not save the second as Federer attacked and hit a lunging overhead of his own for a winner.
Sitting in his chair, Djokovic appeared drawn and weary, breathing hard, his lips parted. "Last five or six days I haven't been feeling that great, but I don't want to talk about it right now," Djokovic said later.
Djokovic declined to elaborate, but he did seem low on energy, even inspiration, as the match progressed.
Paes-Vesnina in mixed semis
Leander Paes and his partner Elena Vesnina, on Friday, stormed into the semifinals of mixed doubles competition after a straight set win over Paul Hanley Alla and Kudryavtseva.
The Indo-Russian pair took just 57 minutes to record a 6-2, 6-2 win.
Paes and Vesnina will take on the winner of the match between top seeds Bob Bryan and Liezel Huber and eighth seeds Daniel Nestor and Julia Goerges. Paes-Vesnina converted four of the five chances that came their way but their rivals failed to convert even one of the two opportunities they got.