Wuhan - Former world No 1 Ana Ivanovic and defending champion Petra Kvitova joined the list of upsets at the Wuhan Open on Wednesday, both falling in the third round.
The pair's losses come on the heels of a series of medical problems and injuries at the tournament that have seen Maria Sharapova, Caroline Wozniacki and Victoria Azarenka exit as the long season begins to take its toll.
Sharapova announced her withdrawal from next week's China Open in Beijing, raising questions over whether the five-time grand slam winner will manage a comeback this season - injuries have kept her off the court since Wimbledon.
Ivanovic fell to Garbine Muguruza, winning the first set but only taking only one game off the Spanish youngster in the second two.
"I had some chances to come back in the second set which I didn't use, and she played well in the big points," said Ivanovic.
The 21-year-old has had a breakout year, joining the ranks of the top 10 for the first time after reaching the Wimbledon finals this year.
Muguruza is in the running to make it to the top-eight Women's Tennis Association Finals in Singapore at the end of this month, with the field looking increasingly open after the Wuhan upsets.
"First set, I lost. I was a little bit disappointed. I said, look, I'm going to fight again and see what happens. I found my game again," said Muguruza.
Kvitova fell to this year's shock finalist at the US Open, Roberta Vinci of Italy, in two sets.
The double Wimbledon champion got off to a strong start, establishing a 4-0 lead over Vinci.
But the Italian clawed back, taking the first set in a tie break, and Kvitova struggled in the second - eventually losing on a break of serve.
"I think she's playing with a lot of confidence right now after such a big win against Serena (Williams), playing the (US Open) final," Kvitova said of Vinci, who returned to the top 20 after her performance at Flushing Meadows.
The Czech was diagnosed with glandular fever this year but has continued to compete, and looked tired as she walked off court.
She said she would now travel to Beijing for next week's China Open, the final tournament before the season finale in Singapore.
Venus Williams took just two sets to dismiss Carla Suarez Navarro of Spain 6-3, 6-4 - potentially setting her up to meet her sister Serena's US Open nemesis Vinci in the semis, if they both make it through the quarter-finals.