Fourth seed Maria Sharapova suffered a third-round loss to Swiss qualifier Timea Bacsinszky in the Wuhan Open in China.
Bacsinszky, 25, won 7-6 (7-3) 7-5 to earn the biggest victory of her career - her other two previous wins against top-10 players were both by retirement.
Russia's Sharapova, 27, double-faulted six times in the first set.
She was also twice a break up in the second set before world number 61 Bacsinszky prevailed.
World number 61 Bacsinszky knocked out US Open semi-finalist and 13th seed Ekaterina Makarova in the second round. She will now face eighth seed Caroline Wozniacki - who swept aside Australian Casey Dellacqua 6-0 6-3 - in the quarter-finals.
Sharapova's early exit followed the withdrawal of world number one Serena Williams from the inaugural £1.5m hard-court event on Tuesday because of a viral illness and second seed Simona Halep's surprise defeat.
France's Alize Cornet, who benefitted from Williams' withdrawal in her last match, beat Belgium's Kirsten Flipkens 7-6 (7-4) 1-6 6-3, while Germany's Angelique Kerber earned a straight-sets victory over Czech Republic's Barbora Zahlavova Strycova.
Sixth seed Eugenie Bouchard of Canada eased past American Alison Riske 6-2 6-3 and will play Cornet in the next round.
Caroline Garcia of France, Petra Kvitova of the Czech Republic and the Ukraine's Elina Svitolina are also through to the quarter-finals.