MELBOURNE, Australia -- World No. 1 Caroline Wozniacki and 14th-seeded former No. 1 Maria Sharapova moved into the fourth round, while former top-ranked stars Venus Williams and Justine Henin exited the 2011 Australian Open on Friday.
The Danish Wozniacki took advantage of 41 unforced errors to defeat 29th- seeded Dominika Cibulkova 6-4, 6-3 in 1 hour, 32 minutes at Melbourne Park. The 20-year-old Wozniacki won five-of-10 break points against her Slovakian counterpart.
"I felt great out there today on the court," Wozniacki said. "You know, I think I played a pretty good match. I am happy I got the revenge since I lost to her in Sydney last week. It was not an easy match."
The 2009 U.S. Open finalist Wozniacki will meet Latvian Anastasija Sevastova, a 6-1, 6-3 winner over Vesna Manasieva of Russia, in the fourth round.
The fourth-seeded Williams was trailing 30th-seeded German Andrea Petkovic 0-1 in the opening set on Friday when the seven-time major champion retired due to an injury after playing only seven points. This marked the first time that Williams retired from a Grand Slam match.
In the second game against Petkovic, Williams cried out in pain after returning a serve. She then clutched her right side and decided that her fortnight was over.
"Obviously I just couldn't play," Williams said. "I couldn't move, it was too painful."
The 30-year-old Williams entered Friday's match with her right thigh heavily taped because of an injury she suffered in the first set of her second-round match on Wednesday. She said her latest injury was in her "psoas" muscle, which flexes the hip and spinal column.
"The last 48 hours, I just did as much pain management as I could," she said. "A lot of times when you play, you get that adrenalin and that blocks pain. I just didn't get enough of that today. I was hoping for some magic that I could recover."
"It's super disappointing because this is just not how I envisioned my Australian Open being," Williams added. "But I have peace of mind that I really gave more than my best to be out there."
"I'm just going to focus obviously on getting healthy and coming back, because I love tennis and I've got a lot of great tennis in me. I love my job, so no end in sight."
Petkovic was stunned by the sudden end to the bout.
"I feel very weird about how the things went," Petkovic said. "It's a pity, and I feel very sorry. I just hope she gets better, she's such a great champion."
Williams has never titled in Melbourne, where she was the 2003 runner-up to her younger sister Serena, who skipped this 2011 Aussie fortnight because of an injury of her own.
Meanwhile, 23rd-seeded former top-five Russian Svetlana Kuznetsova upended the 11th-seeded Henin 6-4, 7-6 (10-8). Henin was last year's Aussie Open runner-up to Serena.
The Belgian Henin, the 2004 Australian Open champion, landed only 57% of her first serves and committed 41 unforced errors in falling to Kuznetsova for just a third time in 19 meetings.
"Well, of course it's disappointing to lose like this," the seven-time Grand Slam winner Henin said. "She is just been better than me, especially in the important moments. I got some opportunities in the second set to come back, but I never really took the lead in this match."
Henin was also a Melbourne runner-up in 2006.
Kuznetsova will next do battle with Italy's Francesca Schiavone, a 6-0, 7-6 (7-2) winner over Romanian Monica Niculescu. The sixth-seeded Schiavone is the reigning French Open champ.
Sharapova dropped the first set before bouncing back to defeat German Julia Goerges 4-6, 6-4, 6-4.
The Russian Sharapova committed 29 unforced errors and 11 double faults, but found a way to defeat Goerges for a second time in as many meetings. The 23- year-old Russian popped six aces and cashed in four-of-six break-point opportunities on Day 5.
Sharapova, who captured the Aussie Open in 2008 and was the 2007 runner-up to Serena, will meet Petkovic in the fourth round.
Other winners Friday were ninth-seeded Chinese Li Na, who defeated Czech Barbora Zahlavova Strycova 6-2, 6-1, and eighth-seeded Belarusian Victoria Azarenka, who pasted South African Chanelle Scheepers 6-3, 6-3. Li was an Aussie Open semifinalist last year and upset Kim Clijsters in a final in Sydney last week.
Azarenka and Li will do battle here on Sunday.
The third round will wrap-up on Saturday, including matches for second- seeded U.S. Open and Wimbledon runner-up Vera Zvonareva, a third-seeded U.S. Open champion Clijsters and fifth-seeded 2010 French Open runner-up Samantha Stosur of Australia. Zvonareva will take on 31st-seeded Czech Lucie Safarova, while the 2004 Aussie Open runner-up Clijsters will encounter France's Alize Cornet and Stosur will battle 25h-seeded Czech Petra Kvitova, a surprise Wimbledon semifinalist last summer and titlist in Brisbane two weeks ago.
