Wuhan - Britain's Johanna Konta pulled off a stunning third-set revival on Wednesday as she floored top seed Simona Halep in the biggest upset yet at the shock-prone Wuhan Open.
As defending champion Petra Kvitova joined the exodus of top seeds, world number two Halep, appeared to have the measure of 66th-ranked Konta when she led 5-1 in the third.
But 24-year-old Konta, who reached the US Open last 16 as a qualifier, bravely fought her way back to take it 6-3, 3-6, 7-5 and set up a quarter-final with childhood idol Venus Williams.
"I wasn't actively thinking 'I can win this' or 'It's over'. I was just trying to stay out there as long as possible and keep fighting every single point," Konta said.
She added that she grew up watching Williams, the seven-time Grand Slam title winner and that the chance to play the American was "a bit of a childhood dream".
Konta will now overtake Heather Watson to become Britain's number one, and will almost certainly move into the world's top 50 when new rankings are released on Monday.
She is also the first British woman to beat a world number two in 34 years after Sue Barker won against Tracy Austin in Brighton in 1981.
Halep said: "I can say I was dominating the third set till 5-2, then I don't know what happened. I have no idea. What I know is that I lost from 5-2."
It was the most remarkable result so far of what has been a highly unpredictable tournament in central China after a rash of upsets and retirements.
Last year's winner Kvitova had looked exhausted after Tuesday's three-set tussle with Daria Gavrilova, and it was no surprise when she went down to US Open finalist Roberta Vinci.
The Czech led 4-0 in the first set but she eventually lost the opener in a tie-break and then struggled in the second as Italy's Vinci took it 7-6 (7/3), 6-2.
"I think she's playing with a lot of confidence right now," Kvitova said of Vinci, who ended Serena Williams' bid for a calendar-year Grand Slam to reach the US Open final.
Vinci said: "The court was for me slow and also the ball heavy. (It) was difficult for me to push a lot. But, of course, I'm really happy."
With Maria Sharapova, Victoria Azarenka, Caroline Wozniacki, Belinda Bencic also departing early, Ana Ivanovic became another big name to fall when she lost Garbine Muguruza.
The Serbian former world number one won the first set, but it was one-way traffic thereafter as Muguruza suddenly rediscovered her mojo and romped home 4-6, 6-1, 6-0.
"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 the hard-hitting Spaniard.
Muguruza, currently ranked eighth, is among several players in the running to reach this month's eight-player WTA Finals in Singapore, where at least five places remain up for grabs.
Kvitova, who was hit by glandular fever this year and was visibly tired as she left court confirmed she would play next week's China Open as she bids to qualify for the WTA Finals.
But Sharapova, who retired with an arm injury in Wuhan and has not completed a match since July, will not defend her title in Beijing, leaving her participation in the Finals in question.
"I am very disappointed to have to pull out of the China Open this year and not have the chance to defend my title," the Russian said in a statement.