(CNN) -- Russian Nadia Petrova on Sunday upset one of the Australian Open tournament favorites after beating compatriot Svetlana Kuznetsova 6-3, 3-6, 6-1.
No.3 ranked Kuznetsova committed 52 unforced errors compared to 22 winners, while Petrova recorded 47 and 25 respectively.
"I was struggling with finding my rhythm the entire match," Kuznetsova told the Australian Open Web site.
"I give credit to (Petrova). It's the best I've seen her play last two years I think, but I didn't deserve to win because I was not playing good enough. I had too many unforced errors and didn't serve good."
On Saturday, defending champion Serena Williams cruised into the fourth round after a comfortable win over Spain's Carla Suarez Navarro in straight sets.
The world number one possessed greater power and a wider range of shots than Navarro as she wrapped up the 6-0, 6-3 victory in 80 minutes to set up last-16 meeting with Australian Samantha Stosur who defeated Italy's Alberta Brianti 6-4, 6-1.
Williams was pleased with her performance but admitted she is yet to hit top form in the tournament.
"I felt like I played okay. I still feel like I can do better. I think my forehand was solid today. I liked it today a lot," Williams told the Australian Open Web site.
Sister Venus Williams also had a relatively smooth passage to the fourth round after a 6-1, 7-6 (7-4) win over Casey Dellacqua. Next up for Venus is Francesca Schiavone after the 17th seed claimed a superb 6-2 6-2 victory over 10th seed Agnieszka Radwanska.
Danish teenager Caroline Wozniacki is on course for a quarterfinal meeting with sixth seed Venus after the world number four set up a last-16 clash with Li Na following a composed 6-4 6-0 win over Israel's Shahar Peer.
Kim Clijsters crashed out of the tournament along with eighth seed Jelena Jankovic, but fellow former world number one Justine Henin continued her winning return to tennis.
Clijsters, who stunned the sporting world with victory at the U.S. Open in September three tournaments into her own comeback, was one game away from a whitewash defeat by Petrova in her worst result as a professional.
Clijsters, who committed 26 unforced errors to her opponent's 10, suffered her worst result in Melbourne since her first appearance in the Victoria state capital in 2000. She had reached the semifinals or better in her last five visits.
Kuznetsova, the 2004 U.S. Open champion, had to come from behind to defeat Germany's Angelique Kerber 3-6 7-5 6-4.
Petrova will now play Henin, who fared better than her compatriot Clijsters on Friday but had to dig deep before beating big-hitting Russian 27th seed Alisa Kleybanova 3-6 6-4 6-2.
Kleybanova, who beat Jelena Dokic in the first round, led 3-1 in the second set before her opponent rallied to win in two hours and 23 minutes.
It was another strong workout for the seven-time Grand Slam winner, who is playing only her second event since coming out of retirement and who needed three hours to defeat fifth seed Elena Dementieva in the previous round.
She won a total of 96 points to Kleybanova's 90, and had only two fewer unforced errors.
"I'm happy I'm in the fourth round. I kind of survived a little bit today," Henin said. "It's always good to win this kind of match because I came back from nowhere.
"It was so difficult for me after last match. Physically, I suffered a little bit in the last two days. I wasn't feeling the energy enough to be able to compete at my level."
Henin will next play fellow Belgian Yanina Wickmayer, who defeated Italy's Sara Errani 6-1 6-7 (4-7) 6-3.
Former world number one Jankovic, who reached the semifinals in Melbourne two years ago, was crushed 6-2 6-3 by Ukrainian 31st seed Alona Bondarenko.
The Serbian made 40 unforced errors and served four double-faults as she lost to Bondarenko for the first time in 10 meetings.
"Unfortunately today really wasn't my day," she said. "You know, I was hitting some balls short, and then some balls I went for maybe a little bit too much. I made a lot of errors that I shouldn't have made."
Bondarenko will next play China's Zheng Jie, who upset 11th seed Marion Bartoli of France 5-7 6-3 6-0.
World number two Dinara Safina cruised into the fourth round with a 6-1 6-2 win over unseeded Elena Baltacha of Britain, and is set to face Russian Maria Kirilenko who progressed with a 7-5 7-6 (7-4) victory against Italy's Roberta Vinci.