MELBOURNE, Australia - When Serena Williams went over on her right ankle against Edina Gallovits-Hall on Tuesday, it was feared that the injury would put paid to her doubles campaign with sister Venus as well as endanger her participation in the singles.

But, five days later, Serena is still fighting on both fronts, with victory over No.5 seeds Nadia Petrova and Katarina Srebotnik taking her and Venus to within three wins of a fifth Australian Open doubles crown.

And after their 62 63 victory in the third round, Serena was quick to emphasize doubles' importance to both herself and her sister.

"I mean, people that are winning a lot of singles titles, nowadays, in the past decade or two decades, usually don't win as many in doubles," she said. "Now I'm almost even with my singles and doubles.

"I think that's really cool. It shows that we're really all-around players."

She was also quick to point out that despite leading the way on the singles court, she still defers to her older sister when they join forces.

''She serves first. She's been the leader since we played back in the '80s when we were juniors,'' she added. ''I'm not comfortable being the leader - I don't want to be the leader!"

While the Williamses are yet to drop a set in Melbourne, many of their chief rivals for the title have fallen by the wayside - with four third round matches still to play, only three of the Top 10 seeds are still in the draw.

Among the three surviving teams are top seeds Sara Errani and Roberta Vinci. The Italians, who finished as runners-up last year, will play the Williamses next, although they were made to work hard for their place in the last eight, eventually seeing off Hsieh Su-Wei and Peng Shuai, 64 06 75.

Also advancing were Sílvia Soler-Espinosa and Carla Suárez Navarro and the No.4 seeds, Ekaterina Makarova and Elena Vesnina.