Karolina Muchova ended Aryna Sabalenka's 15-match winning streak in the China Open semi-finals in Beijing.
The US Open champion was bidding for a third straight tournament victory and led 4-2 in the deciding set but Czech Muchova fought back to win 7-6 (5) 2-6 6-4.
It was a third successive victory over Sabalenka for Muchova, who has been in impressive form since returning in June after more than 10 months out following wrist surgery.
Meanwhile, world number one Iga Swiatek has announced she has split from her coach of three years Tomasz Wiktorowski.
Writing on Instagram, the Pole said: "After 3 years of the greatest achievements in my career, together with my coach Tomasz Wiktorowski we decided to part ways."
Swiatek won four grand slam titles under the tutelage of Wiktorowski and established herself as the dominant force in women's tennis but she has not lifted a trophy since the French Open in June.
She revealed she is in talks with a "non-Polish" coach and will miss next week's Wuhan Open while she searches for a new mentor.
Swiatek is the third high-profile women's player to change coach in a matter of weeks after Naomi Osaka, who split from Wim Fissette before starting work with Patrick Mouratoglou, and Coco Gauff, whose partnership with Brad Gilbert came to an end.
