- French Open champion Li Na loses to world No. 142 in the fourth round
- Kazakh qualifier Yaroslava Shvedova moves into the quarterfinals in Paris
- World No. 2 Maria Sharapova battles into the last eight with three-set win
- Russian will go top of the rankings if she reaches the title match
Li Na's French Open title defense came to a shock end on Monday as the Chinese tennis star followed world No. 1 Victoria Azarenka in exiting the clay-court grand slam.
With second-ranked Maria Sharapova struggling into the quarterfinals with a labored victory, the way is open for the lesser lights of the women's game to make a name for themselves.
Li had been hoping to become the first player since Justine Henin in 2007 to successfully defend her title, but the world No. 7 lost 3-6 6-2 6-0 to Kazakh qualifier Yaroslava Shvedova -- ranked 135 places below her.
"I lost one match so don't try to put me down," she said angrily at the post-match press conference.
"I will try to find the reason why I lost. I will take some days off to totally forget tennis, then try to come back next week. I need some time to recover, I'm not a machine."
Sharapova also battled with the cold, windy conditions at Roland Garros as her serve fell apart and she made a series of unforced errors before finally beating unseeded Czech Klara Zakopalova 6-4 6-7 (5-7) 6-2.
The Russian is seeking to win the tournament for the first time, having reached the semifinals last year and in 2007, and she will displace Azarenka at the top of the rankings if she makes it to the title match.
She has not won a grand slam since 2008, when she added the Australian Open to her U.S. Open and Wimbledon crowns.
The 25-year-old has resurrected her career after longterm shoulder problems, but major doubts remain about the consistency and strength of her serve -- which let her down in last year's Wimbledon final defeat by Petra Kvitova and again in the title match against Azarenka in Melbourne in January.
The match with Zakopalova featured an incredible 21 breaks of service as Sharapova delivered 12 double-faults to her opponent's seven and 53 unforced errors to the 30-year-old's 48.
"The conditions were difficult today, but it was a good test," said Sharapova, who lost only five games in her previous three matches.
"I had the chance to finish it in two. I came out strong in the third set and it's nice to be in the quarters again."
Sharapova will next face Estonian 23rd seed Kaia Kanepi, who upset former world No. 1 Caroline Wozniacki in round three and then beat unseeded Dutchwoman Arantxa Rus on Monday.
Kanepi won 6-1 4-6 6-0 against the 21-year-old conqueror of Germany's No. 25 Julia Gorges to match her 2008 effort of reaching the quarters.
Shvedova's reward for toppling Li is a clash with Czech fourth seed Kvitova , who thrashed Uzbekistan-born American Varvara Lepchenko 6-2 6-1 to reach the event's last eight for the first time.
The 24-year-old Shvedova also reached quarterfinals in Paris in 2010, when she won grand slam doubles titles at Wimbledon and the U.S. Open. However, she was a first-round loser here last year and then at Wimbledon and missed the other two majors as she struggled with injuries.
After Sharapova and Kvitova, the highest-ranked player remaining in the last eight is U.S. Open champion Sam Stosur.
The sixth-seeded Australian, who was runner-up in Paris in 2010, will next face Azarenka's conqueror Dominika Cibulkova.
Tuesday's other quarterfinal will be between German 10th seed Angelique Kerber and Italy's No. 21 Sara Errani.