Muchova saved two set points in the first set and won 7-6(7-5),2-6,6-4. Sabalenka, who this year won the Australian Open and US Open Grand Slam tournaments, had not lost since the quarter-finals in Toronto at the beginning of August.
Muchova is a bad fit for Sabalenka and this was the third straight loss for the Belarusian world number two, whose 15-match winning streak was a personal best for her.
49-ranked Muchova won the last ten points after turning 2-4 in the set. Muchova, whose main achievement is a place in the French Open final last year, heaped praise on Sabalenka before commenting on her own performance.
The Olympic champion awaits in the semi-finals
– I think I have gotten better too and fought for every ball. Somehow I felt pretty good on the track. Of course I still need to work on my fitness – I didn’t have much time to work on it this year, says Muchova according to the WTA.
In the semifinals, Muchova will face Chinese Olympic champion Zhengi Qinwen, who beat 17-year-old Russian Mirra Andreeva 5-7,6-0,6-4.
In the second semi, Coco Gauff and Paula Badosa meet.