Beijing - Ukrainian Elina Svitolina scored her second win this year over a world number one, ousting Angelique Kerber in the round of 16 in Beijing on Thursday.
Nineteenth-ranked Svitolina took just two sets to beat newly crowned number one Kerber - who ascended to the top spot at the US Open, the same week she also claimed her second Grand Slam crown - with a 6-3, 7-5 win.
The 22-year-old left Serena Williams in tears in Rio in August, denying the 22-time Grand Slam champion a fifth Olympic gold medal with a straight set win.
Kerber, who had her right thigh taped, had a break lead in each set but appeared glued to the baseline during the match and was unable to take control.
"I know that I have to move very well when I play my game, and I couldn't play my game like I play," Kerber told reporters after the match.
The German still plans to play in Hong Kong next week as she chases points to end the year at number one - but her right leg may alter her plans.
"Still it's in my schedule to play Hong Kong. It's right after the match, so I don't know exactly with my leg or whatever. But it's still in my schedule," she said.
Briton Johanna Konta secured her first ever win over US Open finalist Karolina Pliskova in a three set tie break, 6-1, 3-6, 7-6 (7/2).
With a victory over the sixth-ranked Czech, Konta - currently at number 14 - moves closer to breaking into the top ten for the first time.
The win also moves the 25-year-old into tenth position in the race for the eight-player WTA Final in Singapore, meaning she could play if one of the eight dropped out.
But if fellow quarter-finalist Petra Kvitova, currently 12th in the race, continues her stellar Asian run, the Briton could be nudged out.
Agnieszka Radwanska secured her second consecutive win over former number one Caroline Wozniacki to reach the China Open quarter-finals.
The pair have met three times in as many weeks, with Wozniacki coming out on top in the first encounter in Tokyo.
Wozniacki went on to bag the title in the Japanese capital, but Radwanska ended her seven-match winning streak at last week's Wuhan Open by ousting the Dane in the round of 16.
Third-ranked Radwanska booked her Beijing quarter-final spot on the third match point with an impressive run to the net to return a drop shot from the Dane. Wozniacki lobbed the return, but the Pole made it to that one to take the match 6-3, 6-1.
"I knew nothing's going to come for free. I was really trying to be aggressive from the first point and also from the return," Radwanska told reporters.
"We know each other for 17 years. Practising together as well almost every tournament, playing some matches against each other. I think we know about each other everything," she added.
Results from the ATP/WTA China Open in Beijing on Thursday (x denotes seeding):
Elina Svitolina (UKR x16) bt Angelique Kerber (GER x1) 6-3, 7-5
Daria Gavrilova (AUS) bt Caroline Garcia (FRA) 6-4, 6-3
Agnieszka Radwanska (POL x3) bt Caroline Wozniacki (DEN) 6-3, 6-1
Johanna Konta (GBR x11) bt Karolina Pliskova (CZE x5) 6-1, 3-6, 7-6 (7/2)