Serena Williams rallied from a break down in both sets on Monday to beat Australian Sam Stosur 7-5 6-3 and advance to the quarterfinals of the Miami Masters.

Williams, bidding for a record sixth Key Biscayne title, avenged a loss to Stosur when they last met in the US Open final in September.

Ranked 11th, Williams is playing in her first tournament since January after being sidelined by a left ankle injury.

She hit 20 aces and lost only six points on her first serve, but she had to rally after being broken in the first game of each set against the No.5-ranked Stosur.

Williams, seeking her first tournament title since August, has won five consecutive matches when facing top-five players.

Earlier, Maria Sharapova survived a brief lapse but regained control in time to post a 6-4 7-6 (7-3) defeat of fellow Russian Ekaterina Makarova for a place in the quarter-finals.

The second seed was cruising when her game went off the boil in a fourth-round match not helped by 11 double-faults in the sun-baked conditions at Crandon Park.

“I was up a set and a break and played a bit sloppy,” said the three-time Miami losing finalist who was beaten for the title last year by Victoria Azarenka.

“It was a combination of her stepping up and being much more aggressive.

“She had opportunities, she served for the second set. But I just hung in there and stayed consistent. I played a much smarter tiebreaker, and I think that helped me extremely.

“I managed to win the match in two sets, so that’s a plus.

Consistency will be really important in the next match and getting the percentage up and also returning a little bit better, little things here and there.”

Sharapova will next face the winner from China’s eighth seed Li Na and German 12th seed Sabine Lisicki.

French seventh seed Marion Bartoli reached the last eight after she beat Russia’s Maria Kirilenko 6-1 6-2.

In the men’s third round, Mardy Fish hung onto the top national ranking place through his defeat of South African Kevin Anderson 6-4 6-3. The victory, which came only hours after challenger John Isner crashed out in the event, was played on a secondary showcourt,

Fish, eighth in the world, has been complaining that even with his national status, he has yet to play on a showcase court so far this month at Indian Wells and Miami.

Spanish 12th seed Nicolas Almagro beat compatriot Fernando Verdasco 6-3 6-4 while Frenchman Richard Gasquet defeated Albert Ramos 6-2 5-7 6-3.