MELBOURNE, Australia (AP) -- Serena Williams may have rolled her ankle, and whacked herself in the lip with her racket, but that doesn't mean she needs any extra rest.
A day after winning her third-round match against Ayumi Morita of Japan -- her first-injury free round at this year's Australian Open -- the No. 3-ranked Williams was back on the court Sunday to play alongside sister Venus.
The Williams sisters take doubles seriously, and that can mean skipping the rest day between singles matches. Venus has joked they have so many trophies they use some as fruit bowls.
The sisters have captured 13 major doubles titles, including four at the Australian Open. They've also won three Olympic gold medals for doubles.
So dominant are Venus and Serena, they've never lost in a Grand Slam doubles final they've contested. They've reached the final in seven of the last 10 majors they've played.
"They mean a lot to me," Serena said earlier this week of her doubles titles from Grand Slams.
"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. So I'm almost even with my singles and doubles."
Serena has 15 major singles titles, while Venus has seven.
Because they tend to only play doubles in the slams, the sisters don't have high rankings in the event. This means they usually have a low seeding -- much to the chagrin of the top-ranked doubles teams in the world.
The Williams sisters were seeded 12th at the Australian Open, which led to an early third-round encounter with the unlucky fifth-seeded team of Nadia Petrova and Katarina Srebotnik on Sunday. The sisters won 6-2, 6-3.
Serena may be the more accomplished singles player in the family -- Venus lost her second-round singles match to No. 2 Maria Sharapova -- but on the doubles court she defers to her older sister.
"She serves first. She's been the leader since we played back in the '80s when we were juniors," Serena said, nodding to Venus, after their win on Sunday. "I'm not comfortable being the leader, I don't want to be the leader."
MOVING ON UP: David Ferrer will bypass injured Rafael Nadal to reach No. 4 in the rankings after the Australian Open, but he still doesn't feel he's that close to the Big Four of men's tennis.
Ferrer, ranked fifth at the end of the last two years, is one of the best active players never to have won a major. The Spaniard has been close. He's reached semifinals three times, including twice last year, but has never been in a final.
The Big Four -- Roger Federer, Novak Djokovic, Nadal and now Andy Murray -- have combined to win 33 of the last 34 majors. Only Juan Martin del Potro has broken the stranglehold to win one at the 2009 U.S. Open.
Now, Ferrer may have his best shot.
He's coming off a career-best 2012 season in which he won seven titles -- more than any of the Big Four. And Nadal is absent from this year's Australian Open because of injury and illness.
After dismantling Kei Nishikori of Japan 6-2, 6-1, 6-4 on Sunday to reach the quarterfinals here for the third straight year, Ferrer was asked if he believes this is his year to finally raise a trophy.
"I don't know," Ferrer said. "Is very difficult to win a Grand Slam because there are the top four. In this moment, the last three or four years, they are better than the other players."
But does he feel he's closing the gap?
"No, no. I think the top four, they are better," he insisted.
HELPING A FRIEND: Tennis greats are teaming up for a charity auction to raise money for retired player Andrew Florent, who was recently diagnosed with cancer.
Among the items being auctioned are a private tennis lesson with Jim Courier and a doubles match against Pat Rafter and Goran Ivanisevic, Tennis Australia said in a statement.
Fans can bid for two seats at the so-called Legends Lunch on the Saturday of the women's final, which will be attended by Rod Laver and Andre Agassi.
Agassi, an eight-time Grand Slam winner who won his last major at Melbourne Park in 2003, will also be taking part in the men's pre-final ceremony on Sunday, tournament organizers said.
Among other items on the block are a pair of tickets to both the men's and women's final as well as a photo opportunity beside the men's winner on Sunday.
The 42-year-old Florent, the 1988 runner-up at the Australian Open junior singles tournament, turned pro in 1990 and became a doubles specialist who achieved a career high ranking of 13 in 2001.
The statement described him as "one of the most popular players on the tour."
"This is terrible news, but what has heartened Florey and his family has been the outpouring of support from the entire tennis fraternity," said friend and former Australian player Paul Kilderry.
The online auction at http://bit.ly/VQ3dBm. closes Thursday at 5:15 p.m. local time.
Associated Press writer Jocelyn Gecker contributed to this report.