Australian Open champion Victoria Azarenka, French Open titlist Maria Sharapova and Wimbledon winner Serena Williams were a trio of third-round winners Wednesday at the Olympic Tennis Event.

The Belarusian Azarenka was pushed in a gritty 7-6 (8-6), 6-4 victory over 16th-seeded Russian Nadia Petrova on Court 1 at the storied All England Club.

Azarenka, who has spent the majority of 2012 at No. 1 after capturing her first major title in Melbourne back in January, will tangle with tough German left-hander Angelique Kerber on Thursday.

Also on Court 1, the third-seeded former No. 1 Sharapova came from behind to best 15th-seeded German slugger Sabine Lisicki 6-7 (8-10), 6-4, 6-3. The Russian superstar avenged a straight-set fourth-round Wimbledon loss here at the hands of Lisicki last month.

Sharapova is now a flawless 10-0 in three-set matches this year and 22-1 in three-setters over the last two seasons.

The 25-year-old Sharapova's quarterfinal opponent will be fellow former top- ranked star Kim Clijsters of Belgium.

Meanwhile, the fourth-seeded former No. 1 Williams lambasted 13th-seeded Russian Vera Zvonareva 6-1, 6-0 on the famed Centre Court. The rout was over in 51 minutes, as the powerful American fired 12 aces, did not commit a double fault, and struck 29 more winners (32-3) than her helpless Russian counterpart.

Williams also whipped the 2008 Beijing bronze medalist Zvonareva in the 2010 Wimbledon final here at the All England Club.

The 30-year-old Williams, who's now a perfect 10-0 on grass this year, owns 14 major singles titles, including five Wimbledon championships, but still needs an Olympic gold medal to complete a career "Golden Slam."

Her quarterfinal opponent will be eighth-seeded Dane and fellow former top- ranked star Caroline Wozniacki, who handled Slovak Daniela Hantuchova 6-4, 6-2 on Centre Court.

The aforementioned seventh-seeded Kerber doused American Venus Williams in a pair of tiebreaks, 7-6 (7-5), 7-6 (7-5), as Venus had a bad serving day, as evidenced by seven double faults.

Kerber advanced in 1 hour, 49 minutes with the help of 36 unforced errors by Venus, and the German was a perfect 3-for-3 on break-point chances. Venus failed to convert on three set points in the opening stanza.

"I made a few errors and she hit a few winners, and things can go quickly in tennis," Venus said. "Hopefully, there's 2016."

The 32-year-old three-time Olympic gold medalist captured singles gold 12 years ago in Sydney and, like her fellow former No. 1 younger sister, is a five-time Wimbledon champ.

Also on Wednesday, sixth-seeded 2011 Wimbledon champ Petra Kvitova of the Czech Republic cruised into the Olympic quarters with a 6-3, 6-0 pasting of overmatched Italian Flavia Pennetta. The left-handed Kvitova will meet 14th- seeded Russian Maria Kirilenko in the round of eight. Kirilenko moved on with a 7-6 (7-5), 6-3 victory over German Julia Goerges.

And in a battle of former No. 1s, the aforementioned Belgian star Clijsters upended 11th-seeded Serb Ana Ivanovic 6-3, 6-4. Clijsters is a four-time Grand Slam champ, while Ivanovic is a former French Open titlist.

In women's doubles action on Wednesday, a top-seeded American tandem of Liezel Huber and Lisa Raymond handled a sixth-seeded Russian duo of Ekaterina Makarova and Elena Vesnina 6-3, 6-3 to reach the semifinals. The 35-year-old Huber and 38-year-old Raymond are the reigning U.S. Open champs.