SEOUL — Jessica Pegula advanced to her 12th quarterfinal of the season by beating Ashlyn Krueger 6-3, 6-1 on Thursday at the Korea Open.

Pegula will play another American, Claire Liu, in the quarterfinals Friday.

Back Da-yeon, the 569th-ranked wild card who eliminated second-seeded Jelena Ostapenko in the opening round, lost to Kimberly Birrell 6-0, 6-1.

Also, fourth-seeded Marie Bouzkova advanced when Eva Lys retired from the match after losing the first set 6-1 and Emina Bektas defeated Jang Su-jeong 6-3, 6-4 to advance to her second tour-level quarterfinal.

Zhengzhou Open

Ons Jabeur won her opening match at the Zhengzhou Open and advanced to the quarterfinals by defeating Lucia Bronzetti 6-3, 7-6 (5).

The seventh-ranked Jabeur will next play either wild-card Bai Zhuoxuan or eighth-seeded Daria Kasatkina.

Also, Laura Siegemund rallied to beat Liudmila Samsonova 3-6, 6-2, 6-1. The 133rd-ranked Siegemund will play Jasmine Paolini in the quarterfinals.