China’s Zheng Qinwen stunned world number one Aryna Sabalenka 6-4 6-3 to set up an Italian Open semi-final against Coco Gauff.
Olympic champion Zheng, who had lost all six of her previous meetings with Sabalenka, broke the Belarusian’s serve to lead 3-2 before closing out the first set.
The eighth seed then made the crucial break in Sabalenka’s first service game of the second set to open a route to victory.
Sabalenka made impressive holds in the fifth and seventh games of the set, but 22-year-old Zheng held on to secure her first semi-final appearance of the season.
“It’s been a long time I haven’t arrived in semi-finals,” Zheng told Sky Sports.
“It was not easy for me because at the beginning of the year I got some struggle with my arm.
“So right now I’m just perfectly in shape and trying to play better tennis all the time.”
Gauff had earlier defeated Russian teenager Mirra Andreeva in straight sets to march into the last four.
The 21-year-old American, who breezed past Britain’s Emma Raducanu on Monday, continued her impressive run on clay with a 6-4 7-6 (7-5) victory against seventh seed Andreeva.
Former French Open finalist Gauff is guaranteed to become the new number two in the world rankings, overtaking Iga Swiatek, after hitting a rich vein of form on clay to win nine of her past 10 matches.
“A lot of confidence heading into the semi-finals. I think today some points weren’t played at my best, but I still managed to be successful,” said Gauff, who has reached the semi-finals in Madrid for the third time.
Andreeva let her frustrations boil over at 3-3 in the opening set, hurling her racquet to the floor and waving angrily at her team after sending a forehand into the net.
The 18-year-old recovered to break back immediately as Gauff opened up a 5-3 lead, but she was unable to hold serve again as her opponent wrapped up the set.
She looked in danger of letting the match slip away at the start of the second, dropping serve before regaining her focus to fight back and force a tie-break.
However, it was the 2023 US Open champion who edged it as Andreeva sent a backhand long to gift Gauff victory after one hour and 42 minutes.
