China's Zheng Jie knocked top seed Caroline Wozniacki out of the Brussels Open on Wednesday, just hours after prevailing in a three-set opener held over because of Tuesday's heavy rain.
Zheng, the world number 51, eased past the Dane 6-2, 6-4 to reach the quarter-finals.
After Tuesday's washout, 10 first round matches were yet to finish, with all eight second round matches also on the schedule.
But Zheng thrived in the tough conditions, defeating American qualifier Mallory Burdette, 6-2, 4-6, 6-3 in her first round.
Four hours later, she was back on court to beat former world number one Wozniacki.
"She's a very tough player and fought until the last point," said Zheng, who hit 34 winners to the Dane's 17.
Third seed Dominika Cibulkova was also knocked out, falling to Kaia Kanepi, 6-4, 7-6 (8/6) in the first round.
The Estonian later beat Jana Cepelova in her second round match, 6-3, 6-3.
German sixth seed Julia Goerges was also a loser, having to retire with a wrist injury after dropping the first set of her second round match against Romina Oprandi.
China's eighth seed Peng Shuai battled over three hours to edge Olga Govortsova, 4-6, 7-6 (7/4), 7-6 (7/4).
Earlier in the day, Peng beat Sofia Arvidsson 6-3, 6-0 in the opening round.
Hopes of a third Chinese player in the quarter-finals were ended when American fourth seed Sloane Stephens beat Zhang Shuai, 6-4, 6-0.