Federer prevailed 6-3, 5-7, 6-3, on Saturday over Alejandro Falla, a Colombian who pushed him to five sets in the first round at Wimbledon in 2010. The startling momentum swing in the second set was a reminder of how even the game's greats can be vulnerable to a tenacious foe, and their own doubts.
"He hung tough, and I got nervous," Federer said. "It was a tough set to lose for me, particularly in the situation I was in, feeling good and confident about me serving it out. That's the beauty of the game. Sometimes you're one point away, and the next thing you know, you're 25 points away."
Federer is a fourth-time Olympian, and won gold in doubles in 2008. This year, he is aiming for his first gold medal in singles just three weeks after winning Wimbledon and regaining the No. 1 ranking. Serena Williams, who also won Wimbledon, also wants to add a singles gold to her two Olympic doubles titles with sister Venus.
U.S. first lady Michelle Obama watched with the Williams family as Serena beat former No. 1 Jelena Jankovic of Serbia, 6-3, 6-1 at the All England Club, where a looser, more festive atmosphere has replaced the tradition-bound mood of the annual Grand Slam event.
Midway through Federer's match, spectators hoisted their arms successively around the stadium in a so-called "Mexican wave," and some booed raucously when the stunt fizzled out. Federer appeared impassive, but it turned out he was keeping an eye on the crowd.
"To have the Mexican wave going basically after one set is unusual," he said, noting that the crowd did not attempt the same manoeuvre during the entire two weeks of Wimbledon until late in his final against Andy Murray. "It was nice to see. That to me summed it up, that it's a different atmosphere out there."
Federer was never close to defeat against Falla, but twice squandered leads. Falla rallied while serving at 3-5, love-40 in the second set. The Swiss also blew a 2-love lead in the final set, but had the crowd roaring with a succession of deft shots down the stretch.
"It was a pretty much up and down, rollercoaster match, like it was a few years ago," he said, referring to his win over Falla at Wimbledon in 2010. Federer, noted, however, that he has also had emphatic wins over the left-handed Colombian: "I know I can also run through him."
Ranked 51st, Falla said he had to return well to have a chance against Federer.
"I'm sad, because it's always difficult to lose, in any place and against any opponent," he said. "But it was Federer, he's the favourite and I gave everything on the court."
The grass took a troublesome toll. Areas along the baselines reseeded after Wimbledon deteriorated quickly, making the courts slick and causing players to slip and fall.
By the end of the first match on Centre Court, before Williams or Federer stepped onto it, skid marks and barren patches were visible at both ends.
"The grass is a wee bit slippery, but you've just got to deal with it," Williams said. "Get ready to slip and slide, whatever it takes. The area at the net didn't wear out so much. Maybe a lot of the players will start coming to the net."
Four-time Grand Slam champion Kim Clijsters, who won her Olympic debut by beating Roberta Vinci of Italy 6-1, 6-4 on Court 2, said there were no bad bounces but she noticed some problems.
"I felt that the grass is breaking a little faster than during Wimbledon," she said. "There's some chunks, bigger chunks, flying off very early on in the match, which is not the case during Wimbledon."
Much is different about this particular tournament at Wimbledon. The club was more colourful, thanks to purple backdrops and a waiver of the rule requiring players to wear mostly white. Federer donned a red shirt, Williams went with a blue dress and Falla opted for yellow. The day began with a concert by the Pet Shop Boys on the picnic hill overlooking the grounds.
"Wimbledon is so quiet. You know, you don't hear much talking," Williams said. "But here you do hear talking. This atmosphere I didn't expect. It's bananas, and I love it."
Bananas might be a slight exaggeration, but there was a fair buzz with matches on 11 courts.
Former Wimbledon champion Petra Kvitova and former No. 1s Caroline Wozniacki and Ana Ivanovic advanced. Samantha Stosur and Li Na, who won major titles in 2011, were upset in three-set matches.
Crowds were smaller than for Wimbledon, with stands on the outer courts less than half full at the start of play. Centre Court was almost at capacity for Williams' match, although four of the six rows in the Royal Box were empty at one point.
To the left sat Mrs. Obama, who sometimes chatted between points with Venus Williams. Serena had met the first lady before and was advised she would be in attendance.
"They asked me did I mind if she sat in the family box," Williams said. "I was like, 'Of course not. Please, it would be my honour.' I mean, I love Michelle."
As was the case during Wimbledon, Williams won with a dominating serve. She hit eight aces against Jankovic, lost only 10 service points and faced no break points.
The winner of 14 major titles, Williams said the incentive to win the singles is different from a Grand Slam event.
"Let's face it, tennis players play to win Wimbledon," she said. "We play to win Australia. We play to win the U.S. Open. The Olympics is a bonus. So sometimes you get the bonus; sometimes you don't."