Wuhan: Angelique Kerber lost for the first time since becoming the No. 1-ranked player, losing to Petra Kvitova in the third round of the Wuhan Open on Wednesday.
Kvitova saved 17 of 22 break points on her way to the 6-7 (10), 7-5, 6-4 win over Kerber, who committed eight double faults.
"It's always tough to play against Petra," said Kerber, who was facing Kvitova for the 10th time in her career. "I think we both played on a really high level over three hours. At the end, I think there's no loser. I did everything today. I was fighting until the end."
Kerber replaced Serena Williams atop the rankings with her run to the U.S. Open title, and took time off before coming to China to start her Asian swing in Wuhan, where she had a bye in the first round.
Kvitova last beat Kerber in the 2014 Fed Cup final, and had since lost to the German three times, including in the U.S. Open fourth round.
In the quarter-finals, Kvitova will face Johanna Konta of Britain, who beat seventh-seeded Carla Suarez Navarro of Spain 7-5, 7-6 (6). Konta saved three set points in a marathon ninth game, and recovered from 6-3 down in the tiebreak.
Svetlana Kuznetsova ousted defending champion Venus Williams 6-2, 6-2.
Kuznetsova dominated Williams from the outset, breaking the American five times. She improved to 5-4 against Williams.
Williams struggled with her serve in the gusty conditions and had seven double faults.
"I don't think Venus played her best game. But I've been confident and I've been playing well," Kuznetsova said. "I didn't use a couple of my chances in the second set but I still could finish it 6-2."
Kuznetsova next plays third-seeded Agnieszka Radwanska, who beat Caroline Wozniacki 6-4, 6-2.
Simona Halep of Romania also advanced, beating Yaroslava Shvedova of Kazakhstan 6-3, 6-3.
Halep, showing no sign of the hamstring injury that ruled her out of Tokyo last week, will face Madison Keys of the United States in the quarters. Keys beat Russian qualifier Daria Kasatkina 6-1, 4-6, 6-4.