LONDON, July 28 (Xinhua) -- There were some major upsets on the opening day of the London 2012 Olympic Games tennis tournament at Wimbledon on Saturday with sixth seed Tomas Berdych from Czech Republic, Chinese No.1 Li Na and last year's U.S. Open winner Samantha Stosur of Australia all crashing out of the tournament.
World No.7 Berdych was beaten 6-4, 6-4 by world No.75 Steve Darcis of Belgium. Darcis lost in the first round of a second-tier Challenger event just 11 days ago and was playing his first match on Centre Court. At a set and 5-2 up, he needed two attempts to serve out the match and gain his first win over a top 10 player.
Darcis will play Santiago Giraldo from Columbia in the second round after Giraldo defeated Ryan Harrison of the United States 7-5, 6-3.
Another men's seed going out on the first day was Fernando Verdasco from Spain, seeded 14th, who was defeated by Denis Istomin of Uzbekistan 6-4, 7-6(9).
World No.1 and top seed at London 2012, Roger Federer of Switzerland, dropped a set in his match with world No.51 Alejandro Falla of Columbia but eventually won 6-3, 5-7, 6-3. It was not the first time the Colombian had given the Swiss problems: at Wimbledon 2010 he served for the match in the fourth set of their first-round encounter before eventually losing in five sets.
Despite complaints by several players about the state of the courts, Federer dismissed them. He said: "It's always a bit slippery when green. But it's grass, it's supposed to be difficult."
In the second round Federer will play Frenchman Julien Benneteau, who defeated Russian Mikhail Youzhny 7-5, 6-3.
In women's singles, American Serena Williams opened the women's singles on Centre Court with a 6-3, 6-1 win over former world number one Jelena Jankovic of Serbia.
Williams is hoping to add to the two gold medals she won in the women's doubles at Sydney 2000 and Beijing 2008 with her sister Venus Williams, who sat in the players' box with Michelle Obama, wife of the president of the United States, to watch the match.
Kim Clijsters of Belgium had an easy win, taking 61 minutes to defeat Roberta Vinci of Italy 6-1, 6-4. She will meet Carla Suarez Navarro from Spain, who had a shock 3-6, 7-5, 10-8 victory over fifth seed Stosur.
Another seed to go out on the first day was China's Li, the 2011 French Open champion and 10th seed here, who was defeated by Daniela Hantuchova of Slovakia 6-2, 3-6, 6-3.
Other seeds going through to the second round are Ana Ivanovic from Serbia, the 11th seed, who defeated Christina McHale of the United States 6-4, 7-5; and Vera Zvonareva of Russia, the 13th seed and Beijing 2008 bronze medallist, who defeated Sofia Arvidsson of Sweden 7-6(3), 6-4.