But soon-to-be world No. 1 Rafael Nadal kept rolling along.
The rains that disrupted action all around Beijing Thursday forced a long delay at the tennis stadium, where all the men's and women's singles quarterfinals had been scheduled.
Blake pulled off the first surprise by downing Federer 6-4, 7-6 (7-2), beating the current world No. 1 for the first time in his career.
"It means a lot to play with the American flag on your chest," Blake said. "I have been inspired by all the great players here. Not just in tennis, but all through the American team."
Blake moves into the semifinals against 12th-seeded Chilean Fernando Gonzalez, who eliminated France's Paul-Henri Mathieu, 6-4, 6-4, Thursday.
Nadal, who officially knocks Federer from the No. 1 spot effective Monday, advanced to the Olympics semifinals with a 6-0, 6-4 rout of Jurgen Melzer. His semifinal opponent is third-seeded Serbian Novak Djokovic, who rallied for a 4-6, 6-1, 6-4 win over France's Gael Monfils.
Venus Williams soon followed her sister out of the singles draw by losing to China's Li Na, 7-5, 7-5. Venus Williams was trying to win Wimbledon and an Olympic gold medal in the same year for the second time.
Americans Bob and Mike Bryan reached the semifinals with a 6-4, 6-3 victory over Chris Guccione and Lleyton Hewitt of Australia.