(dpa) - Roger Federer and the Williams sisters were eliminated in upsets on a rain-plagued day at the Beijing Olympics Thursday, the Swiss player losing more confidence in a 6-4 7-6 (7-2) loss to James Blake in the quarter-finals.
Federer, who has not won a major title in a year, had been counting on the Games to help revitalize is season. He will now have to swallow disappointment again and aim for the US Open, where he won the trophy a year ago.
Blake finally rose to the occasion after eight consecutive losses to the once-dominant Swiss, including and Australian Open quarter-final at the start of the year.
"I always believed in myself," said the American. "I'd lost to him eight, nine, 10, 50 times, I don't know how many. But I felt it could be my day today."
Russian Elena Dementieva claimed her third straight victory over Serena Williams, striking at the ideal moment with a 3-6, 6-4, 6-3 comeback to knock the American out of the Games.
Williams, who confessed that she could not be bothered last weekend to attend the opening ceremonies, remains alive in doubles with her sister Venus.
But five-time Wimbledon winner Venus was slammed by crowd favourite Li Na in a 7-5, 7-5 victory on the rain-delayed day which stretched well into evening.
China's number 42 Li paid no attention to an early 3-0 Williams lead on the way to the upset to complete the double dismissal of the American siblings.
"This crowd helped me to victory," said the winner. "But I have no time to celebrate. I have more matches to go."
Vera Zvonareva joined Dementieva to pout a second Russian into the semis as she beat Austria's Sybille Bammer 6-3, 3-6, 6-3.
Federer will be desperate after his latest setback, with Rafael Nadal due to replace him after four and a half years on number one with Monday's ATP rankings list.
Nadal and number three Novak Djokovic continued their steady Olympic pace, the Spaniard rolling Jurgen Melzer 6-0, 6-4 and Djokovic rallying past Gael Monfils 4-6, 6-1, 6-4.
Federer is under the cosh in Beijing with a packed-out schedule which includes doubles to be completed by Sunday. That would leave just a week until the start of the Open, final Grand Slam of the season. Federer left no doubt as to his thoughts on the crowded programme: "It's ridiculous that we're playing maybe 11 matches in seven days, to be honest.
"I know it rained the first day, but I don't understand why we don't play such a big tournament over 10 days."
The Swiss goes to New York with his season on the line as he stalls at 12 Grand Slam singles titles.