Samantha Stosur bowed out of the WTA/ATP event in Miami following a straight-sets loss to Serena Williams.
Williams recovered from a break in both sets to beat Stosur 7-5, 6-3 in what was a rematch of last year's US Open final, which the Australian won.
The defeat continues what has been a mixed start to 2012 for Stosur, who is ranked number five in the world.
Williams produced 20 aces but it was not all plain sailing for the former world number one, who lost her first serve of the match but came back to grind out the set in the first meeting between the two players since the US Open decider.
Down 5-2 in the second, Stosur twice saved match point and forced Williams to serve out for the match and although the American trailed 0-40 she booked her spot in the quarter-finals.
"I think for the most part things are working pretty decent," said Williams, who claimed revenge for her defeat at Flushing Meadows had not entered her head.
"I honestly feel like I can do better but my serve was hot and that is pretty cool."
Top seed Victoria Azarenka survived a scare from Dominika Cibulkova, gutting out a 1-6, 7-6 (9-7), 7-5 victory in the fourth round.
Azarenka advances to face France's Marion Bartoli, who easily defeated Maria Kirilenko 6-1, 6-2.
Russian Maria Sharapova also booked a place in the quarters with a 6-4, 7-6 (7-3) win over compatriot Ekaterina Makarova despite being broken four times.
Makarova fought particularly hard in the second set but eventually fell 7-3 in the tie-break.
Sharapova, the runner-up im Miami last year, will face China's Li Na after the French Open champion beat German Sabine Lisicki 3-6, 6-4, 6-2.
Meanwhile, defending champion Novak Djokovic dispatched fellow Serbian Viktor Troicki with a 6-3, 6-4 win to move into the fourth round of the men's draw.
The world number one broke Troicki three times en route to his 11th consecutive win against his compatriot to set up a fourth-round match against Frenchman Richard Gasquet.
Gasquet, who has been a quarter-finalist in four tournaments so far this year, beat Spain's Albert Ramos 6-2, 5-7, 6-3.
Leading American Mardy Fish recovered from being a break down in the first set to defeat 28th ranked Kevin Anderson of South Africa, 6-4, 6-3.
Fish advances to face Spain's 12th seed Nicolas Almagro who played solid tennis, committing just 10 unforced errors in his 6-3, 6-4 win over compatriot Fernando Verdasco.
ABC/ReutersTags: tennis, sport, united-states First posted March 27, 2012 07:36:16