Updated

Reigning champion Maria Sharapova and fellow former world No. 1 Victoria Azarenka were a pair of third-round winners on a sunny, breezy Saturday at the French Open.

The second-seeded Sharapova overcame some sloppy play in order to get past China's Zheng Jie 6-1, 7-5, while the third-seeded Australian Open titlist Azarenka needed all three sets to hold off 31st-seeded French crowd favorite Alize Cornet 4-6, 6-3, 6-1 on the famed red clay at Roland Garros.

Cornet was fresh off her clay-court title in Strasbourg last week.

"She's a machine, a juggernaut," Cornet said of Azarenka. "She plays the same from the first to the last point."

Sharapova, who overcame a 1-4 deficit in the second set against Zheng, completed a career Grand Slam by beating gritty Italian Sara Errani in last year's French Open finale.

Up next for the Russian superstar Sharapova will be 17th-seeded American Sloane Stephens, while Azarenka's fourth-round opponent will be French Open- loving Italian Francesca Schiavone, who blasted 13th-seeded Frenchwoman Marion Bartoli 6-2, 6-1 on Day 7 of the fortnight. The 32-year-old Schiavone titled here in 2010, was the Roland Garros runner-up in 2011, and is now 18-2 in Paris in her last four trips.

Surprising 23-year-old 54th-ranked American Jamie Hampton reached the fourth round of a Grand Slam event for the first time in her career by stunning seventh-seeded former Wimbledon champion Petra Kvitova 6-1, 7-6 (9-7). The Czech left-hander Kvitova, who was a French Open semifinalist a year ago, committed 33 unforced errors in the setback.

Another top-10 upset came when 18th-seeded former world No. 1 Jelena Jankovic of Serbia upended ninth-seeded Aussie Sam Stosur 3-6, 6-3, 6-4. The 2011 U.S. Open champion Stosur was the French Open runner-up three years ago.

The former U.S. Open runner-up Jankovic is a three-time French Open semifinalist and her fourth-round opponent will be the upstart Hampton.

Two other Americans, the aforementioned Stephens and Bethanie Mattek-Sands, reached the round of 16, as the 20-year-old Stephens landed in the fourth round in Paris for a second straight year by outlasting New Zealand's Marina Erakovic 6-4, 6-7 (5-7), 6-3, while Mattek-Sands overcame Argentine Paula Ormaechea 4-6, 6-1, 6-3. Stephens is now 8-1 at the Grand Slams this year, having reached the Aussie semifinals in January.

Stephens, the 28-year-old Mattek-Sands and Hampton joined Serena Williams in the fourth round, giving the United States its best women's fourth-round showing in Paris in nine years.

Also on Saturday, 12th-seeded Russian Maria Kirilenko topped Swiss Stefanie Voegele 7-6 (7-3), 7-5. Kirilenko will meet Mattek-Sands in her next outing.

The fourth round will commence Sunday, including a match for the current world No. 1 and reigning Wimbledon and U.S. Open champion Williams.

The red-hot American, riding a career-best 27-match winning streak, will face 15th-seeded Italian veteran Roberta Vinci on Day 8.

The 15-time Grand Slam singles champ Williams captured her lone French Open title back in 2002.

Also on Sunday, fourth-seeded Wimbledon runner-up Agnieszka Radwanska will battle 14th-seeded former world No. 1 and former French Open winner Ana Ivanovic, a fifth-seeded Errani will take on 20th-seeded Spaniard Carla Suarez Navarro, and eighth-seeded German Angelique Kerber will encounter former Roland Garros titlist Svetlana Kuznetsova.