Shinobu Asagoe tumbled out of the Korean Open in the second round to American Abigail Spears.
The Japanese second seed, who reached the quarter-finals of the US Open but lost her opening match in Beijing recently, was beaten 6-3 1-6 6-3.
But there were no such problems for eighth seed Samantha Stosur.
The Australia cruised past Russia's Galina Voskoboeva 6-2 6-4 and will face either Miho Saeki or Maria Sharapova in the quarter-finals.
Croatian duo Sanda Mamic and Silvija Talaja also went through, with Mamic beating Catalina Castano of Colombia 7-5 6-4 and Talaja rallying to beat Japan's Yuka Yoshida 4-6 6-3 6-0.
Talaja will play Marta Domachowska in the last eight after the Pole defeated Chuang Chia-jung of
Taiwan 7-5 6-1.