Camila Giorgi of Italy stunned Dane Caroline Wozniacki in the second round of the Pan Pacific Open in Tokyo.
It took Giorgi three sets to overcome the defending champion 6-2, 2-6, 6-4 in the Women's Tennis Association Premier Tournament, held at the Ariake Coliseum.
"It was a very good match," Giorgi said.
"This is a nice court and [today] was very fun.
“I was very consistent today, and consistent mentally, so this was important."
The Italian will now play Belarusian Victoria Azarenka in the quarter-finals.
Azarenka beat Australian Ashleigh Barty 6-4, 6-2 to progress.
Britain’s number one female tennis player, Johanna Konta, was defeated by Croatia's Donna Vekic in two straight sets, 6-3, 7-5.
Czech Barbora Strýcová beat Estonian Anett Kontaveit 7-6, 3-6, 7-5.
Vekic will now go on to play Caroline Garcia of France, while Strýcová will play home favourite and recently-crowned US Open Naomi Osaka of Japan.
American Alison Riske and Czech Karolína Plíšková make up the last quarter-final.
The quarter-finals will be played when the tournament resumes tomorrow.