Reigning champion Naomi Osaka of Japan withdrew from the Toray Pan Pacific Open in Tokyo on Thursday due to an illness, giving fifth-seeded Beatriz Haddad Maia of Brazil a win by walkover.
"I am really sorry that I am not able to compete today," Osaka said in a statement. "It's an honor to be able to play at the Toray Pan Pacific Open in front of the amazing fans here in Japan. This has and always will be a special tournament for me and I wish I could have stepped on court today, but my body won't let me."
Haddad will face Veronika Kudermetova in the quarterfinals. The fourth-seeded Russian defeated Mexican qualifier Fernanda Contreras Gomez 6-0, 6-1 in just 56 minutes.
Petra Martic of Croatia upended sixth-seeded Karolina Pliskova of the Czech Republic 6-3, 6-4 to advance. Russian Liudmila Samsonova advanced with a 7-6 (5), 6-3 victory over Xinyu Wang of China.
Hana Bank Korea Open
Top seed Jelena Ostapenko of Latvia needed three sets - and two hours, 35 minutes - to defeat Anastasia Gasanova of Russia 6-3, 5-7, 7-5 in Seoul.
Ostapenko overcame 12 double faults, as well as six aces by Gasanova, to advance to the quarterfinals.
No. 3 seed Magda Linette of Poland rallied to advance with a 4-6, 7-6 (5), 6-2 win over Kristina Mladenovic of France. That match lasted two hours and 46 minutes.
Ninth-seeded Emma Raducanu of Great Britain defeated Yanina Wickmayer of Belgium 6-3, 7-5, and Switzerland's Lulu Sun beat Russian Anna Blinkova 6-4, 7-6 (6).
--Field Level Media