Alison Riske's defence of the Tianjin Open came to an end in a straight-sets defeat to Timea Babos at the WTA International event.
The American, seeded seventh on the hardcourts of the Tianjin International Tennis Centre, was beaten by her Hungarian opponent 6-3 6-3 in one hour 27 minutes.
Riske's victory over Belinda Bencic in the final last year remains her only triumph in a WTA singles tournament and her hopes of retaining the crown are now over after she was broken once in the first set and three times in the second to bow out.
In other matches on Wednesday, fifth seed Kristina Mladenovic of France overcome Poland's Urszula Radwanska 6-4 6-4.
Awaiting her in the last eight is Serbian Bojana Jovanovski, who defeated Russian Elena Vesnina 6-3 6-1.
Several matches, including third seed Karolina Pliskova's meeting with Magda Linette, were suspended due to rain.
