Ekaterina Makarova of Russia moved into the US Open semi-finals after beating 16th-seeded Victoria Azarenka of Belarus 6-4, 6-2 here.
Wednesday night was the first time Makarova entered a Grand Slam singles semi-final, reports Xinhua.
Holding two Grand Slam titles, former World No.1 Azarenka seemed to be the favourite, but Makarova put in a determined performance to leave her opponent shell-shocked.
"I played so many times with Vika, she beat me and I beat her," said Makarova after the match, "So, today was a tough one, and I'm really happy that I came through."