Germany’s Tommy Haas upset world No.1 Novak Djokovic in straight sets 6-2 6-4 on Tuesday to reach the quarter-finals of the Miami Masters tournament.
Haas was facing his first world No.1 opponent since the third round of the 2009 Australian Open, when he lost to Rafael Nadal.
British second seed Andy Murray also booked a quarter-final berth with a 6-2 6-4 triumph over Italian 16th seed Andreas Seppi at the $US8.5 million ($A8.15 million) hardcourt tournament.
Scotsman Murray, the 2009 Miami winner who lost to Djokovic in last year’s final, needed only 86 minutes to book a date in the last eight against Croatian ninth seed Marin Cilic, who beat Frenchman Jo-Wilfried Tsonga 7-5 7-6 (6-4).
Spanish third seed David Ferrer advanced to the quarters with a 6-4 6-2 victory over Japan’s 13th-seeded Kei Nishikori.
Ferrer won 84 per cent of his first-serve points and 5-of-9 break chances to eliminate Nishikori and book a last-eight match against Austria’s Jurgen Melzer, who defeated Spain’s Albert Ramos 2-6 6-3 6-3.
Fifth-ranked Ferrer improved to 3-2 in his meetings with Nishikori, having avenged a round-of-16 loss at the Olympics by defeating him in the fourth round of this year’s Australian Open.
French eighth seed Richard Gasquet outlasted Spanish 10th seed Nicolas Almagro 6-7 (3-7) 7-5 7-6 (7-3) and will face Czech fourth seed Tomas Berdych, who dispatched US 17th seed Sam Querrey 6-1 6-1.
In the women’s draw, world No.1 Serena Williams reached the semi-finals in the WTA event after defeating Chinese fifth seed Li Na 6-3 7-6 (7-5).
Breaking Li three times in each set, Williams fell behind in the second set before roaring back to hold off the Chinese star to end matters after one hour and 50 minutes.
“It’s good to be able to at least come back,” Williams said.
“I like to believe that I try to be a solver. I just try to do things different if something is not working.
“She played such a good tiebreaker. It was important for me to win that.”
Williams had three aces and six double faults to one ace and seven double faults for Li.
“I just can’t hit any more double faults,” Williams said. “It’s embarrassing and unprofessional. I hit about 50 in one game and it was just outrageous. It was like, at this point, I shouldn’t be a professional tennis player.”
Williams improved to 7-1 against Li with her sixth victory in a row, Li’s only win coming at Stuttgart in 2008.
Williams, trying to become the first six-time winner in Miami history, will face defending champion and fourth seed Agnieszka Radwanska of Poland in the semi-finals after she downed Belgian Kirsten Flipkens 4-6 6-4 6-2.
