Former world number one Angelique Kerber was beaten 5-7 6-4 6-0 by unseeded Hsieh Su-wei in the last 16 at the Dubai Championships.
World number 31, Hsieh, who beat Simona Halep at Wimbledon last year, won 12 of the last 13 points to oust the reigning SW19 champion in one hour 44 minutes.
The 33-year-old Taiwanese next faces fourth seed Karolina Pliskova, who beat Alison Riske 7-6 (7-3) 7-6 (7-5).
Third seed Halep saw off Lesia Tsurenko 6-3 7-5 to advance to the last eight.
The 2015 champion, third seed in this year's event, won the first set in just 36 minutes and, after losing her serve in the ninth game of the second, won the next three games.
She will now play 21-year-old Swiss Belinda Bencic, who beat eighth seed Aryna Sabalenka 6-4 2-6 7-6 (9-7).
Sabalenka had six match points before world number 45 Bencic clinched it in two hours 26 minutes with her first.
World number one Naomi Osaka, the reigning Australian and US Open champion, lost in round two to Kristina Mladenovic of France.
Mladenovic's run ended with a 7-5 7-5 defeat in one hour 53 minutes against Spain's Carla Suarez Navarro.
Second seed Petra Kvitova lost the second set 6-1 to American qualifier Jennifer Brady but won the decider 6-3 to wrap up victory in two hours 12 minutes.
Pliskova saved two set points in the second against Riske, who ousted 13th seed Julia Goerges in the opening round, and sealed her win in two hours four minutes when the American double-faulted on match point.
Former Wimbledon champion Garbine Muguruza, the 12th seed, was beaten 6-1 6-2 in an hour and two minutes by sixth seed Elina Svitolina.