Defending champion Li Na was at a loss to explain why she was knocked out by a qualifier in the fourth round of the French Open.
Last year, Li became the first player from China to earn a Grand Slam singles title when she won at Roland Garros. On Monday, she lost 3-6, 6-2, 6-0 to the 142nd-ranked Yaroslava Shvedova of Kazakhstan.
"I have to find the reason why I lose the match," Li said. "I will find out. But not today. Otherwise, for sure, I can win the match. ... I can't find why I couldn't put the ball back on the court."
The seventh-seeded Li dropped the last 10 games and made 41 unforced errors, compared to 21 for Shvedova.
"I need some time to recover," Li said. "I'm not (a) machine."
Shvedova, a doubles specialist who teamed with Vania King to win Wimbledon and the U.S. Open in 2010, offered a theory for Monday's outcome.
"I felt she was nervous a little bit," Shvedova said. "She didn't play maybe like she was playing last year. She was doing some mistakes."
Li has struggled to adjust to her new status as a major champion, which included time commitments for interviews and sponsor appearances.
She now has to handle the pressure coming from the expectations of more than a billion people back home in China. She has not won a tournament since last year's French Open, reaching only two finals in that span.
Li's loss left no past French Open champions remaining in the women's draw.
Shvedova is the only qualifier left in the field.
She became only the ninth qualifier to make it to the quarterfinals at Roland Garros, matching the furthest she's ever been in a Grand Slam singles draw.
Shvedova was hampered by various injuries last season and even fell out of the top 200 in the WTA rankings.
"I had some tough periods mentally. ... I was very down and lonely," Shvedova said. "It's for now the most incredible win, I think, for me."