Wimbledon champions Roger Federer and Serena Williams both made it through to the second round on the opening day of the Olympic tournament at a revamped All England Club on Saturday, albeit in contrasting style.
While Serena produced a polished display in a brutal 6-3 6-1 demolition of
Serbia's Jelena Jankovic, Federer was made to sweat before finally beating
Colombia's Alejandro Falla 6-3 5-7 6-3 on centre court a few hours later.
Federer found Falla a tough customer at Wimbledon for the second time after the Colombian almost caused one of the biggest upsets in tennis history two years ago when he led Federer by two sets to love in the first round at Wimbledon and served for the match, only for the 17-time grand slam champion to turn it around.
Their rematch looked routine for Federer on Saturday when he led 6-3 5-3 and held three match points on Falla's serve, but remarkably he missed them all and was then broken twice in a row to lose the second set.
Falla pegged back Federer again when he went up an early break in the decider but the world No.1 dug deep and pulled through, taking his fifth match point to win.
Federer is favourite to win the Olympic gold, which would be his first in the individual event.
"It was up and down, a rollercoaster match like it was a few years ago," the 30-year-old said.
"I had all the match points I wanted, I served for the match. He got tough and I got nervous. It was a tough set to lose for me.
"That's the beauty of this game. Sometimes you're one point away, the next thing you're 25 points away.
"But I never stopped believing, kept on pushing."
Federer next faces France's Julien Benneteau.
The first match on centre court served up the first upset when Belgium's Steve Darcis knocked out sixth seed and former Wimbledon finalist Tomas Berdych 6-4 6-4.
Belgian Olivier Rochus took on American John Isner who prevailed 7-6 (7-1) 6-4.
Seventh seed Janko Tipsarevic of Serbia and eighth seed Juan Martin Del Potro of Argentina both made it through their opening matches, but Spain's Fernando Verdasco, the 14th seed, was beaten 6-4 7-6 (11-9) by Uzbekistan's Denis Istomin.
In other women's action Belgium's Kim Clijsters enjoyed her first taste of the Olympics as the four-time grand slam champion moved into the second round with a 6-1 6-4 win over Italy's Roberta Vinci.
The 29-year-old next faces world number 45 Carla Navarro Suarez of Spain, who enjoyed a shock 3-6 7-5 10-8 victory over Australian fifth seed Samantha Stosur.
Serbian 11th seed Ana Ivanovic, like Clijsters a former world No.1, also won on her Olympic debut, beating American Christina McHale 6-4 7-5.
But Chinese 10th seed Li Na slumped out, losing 6-2 3-6 6-3 against Slovakia's Daniela Hantuchova.