Key Biscayne, March 28:

Rematches became repeats for Roger Federer and Maria Sharapova at the Sony Ericsson Open here on Tuesday. Both lost.

Guillermo Canas upset top-ranked Federer for the second time this month, 7-6 (2), 2-6, 7-6 (5) in a fourth-round epic. Serena Williams beat Sharapova 6-1, 6-1 in a rout reminiscent of their Australian Open final two months ago. With that, Key Biscayne’s two No 1-seeded players were eliminated.

Two weeks ago, Canas ended Federer’s 41-match winning streak at Indian Wells. The dogged Argentine showed the victory was no fluke, extending points by repeatedly chasing down shots and forcing a frustrated Federer into 51 unforced errors.

The defeat ended Federer’s bid for a third successive Key Biscayne title, while Canas improved to 3-0 this year against top-10 players. Canas was ranked as high as No 8 before serving a 15-month doping suspension, and he had to qualify for the Key Biscayne draw. He’s the first qualifier in nine years to reach the quarter-finals.

Williams, who defeated Sharapova 6-1, 6-2 in the Australian Open final, this time won even more easily. While Sharapova and Federer lost, Andy Roddick won his rematch against David Ferrer. The Spaniard was an upset winner when they played at Key Biscayne a year ago, but this time the third-seeded Roddick won 7-5, 6-3 to reach the quarter-finals.

No 2 Rafael Nadal defeated 18-year-old Argentine Juan Martin del Potro 6-0, 6-4. Sixth-seeded Tommy Robredo of Spain defeated Radek Stepanek of the Czech Republic 7-6 (4), 5-7, 7-6 (3), and No 12 Andy Murray of Britain overcame two match points to beat Paul-Henri Mathieu of France 2-6, 7-5, 6-3. Croatia’s Ivan Ljubicic, last year’s runner-up, fired 13 aces in beating Finland’s Jarkko Nieminen 7-6 (4), 6-4.

Top-ranked Justine Henin reached the semi-finals here for the first time by beating Nadia Petrova 7-6 (4), 7-6 (4). Another Russian Anna Chakvetadze beat Li Na of China 4-6, 7-5, 6-2.