World number two Iga Swiatek is out of the Dubai Tennis Championships after a shock 6-3 6-3 quarter-final defeat by 17-year-old Mirra Andreeva.
The Russian teenager is the youngest-ever player to reach the last four of the tournament.
She was 3-1 down in the second set before reeling off five games in a row to beat Poland’s Swiatek, a five-time Grand Slam winner, in one hour 36 minutes.
Andreeva set up a tie against Kazakhstan’s Elena Rybakina, who defeated the United States’ Sofia Kenin 6-2 7-6 (7-2) later on Thursday.
“Honestly, I was really nervous before the match and we played in Cincinnati last year [which Swiatek won] and it was pretty intense,” Andreeva said.
“So I just told myself that I played great and I just need to continue to play aggressive and go for my shots.
“It was also not easy with all the fans [supporting Swiatek] but I think we were even. I had a lot of people supporting me.”
Victory means the Russian has now beaten both of the world’s top two ranked players in the past 12 months, having defeated world number one Aryna Sabalenka in last year’s French Open quarter-finals.
The teenager becomes the youngest player since Nicole Vaidisova in 2007 to win five matches against players ranked in the top 10.
Meanwhile, Czech Republic’s Karolina Muchova defeated Romania’s Sorana Cirstea 6-2 7-5, and will face Clara Tauson in Friday’s semi-final, following the Dane’s 7-6 (7-4) 6-4 win against Linda Noskova of Czech Republic.
