Duan Ying-Ying was one of three seeds to bow out of the Dalian Women's Open when she was beaten by Aleksandra Krunic
Third seed Duan endured service woes in the WTA 125k hard-court event and went down 6-2 3-6 6-1 to the 153-ranked Serb Krunic.
Krunic will take on Kristyna Pliskova, whose twin sister Karolina will face Serena Williams in the US Open semi-final later in the day, after the Czech got the better of Rebecca Peterson 6-4 6-4.
Tamira Paszek, seeded four, also failed to make it through to the last eight as the Austrian went down 6-2 7-6 (7-2) against Wang Yafan, while sixth seed Jana Cepelova lost 6-4 6-3 to Grace Min of the United States.
Top seed Wang Qiang had no such problems, though, as she dumped out Na-Lae Han 6-3 1-6 6-1, while Han Xinyun, Misa Eguchi and Julia Glushko are also through to the quarter-finals.