TOKYO: Naomi Osaka, seeded No. 7 and playing before home fans in Japan, was knocked out of the Pan Pacific Open on Thursday by Mia Pohankova of Slovakia.
Pohankova, who turned 18 a week ago and was a wildcard entry in Japan, upset Osaka 6-3, 7-5 to advance to the quarterfinals after a match that lasted 1 hour, 35 minutes.
Pohankova will face Alycia Parks in the quarterfinals. Pohankova was the 2025 junior singles champion at Wimbledon.
Osaka was coming off a win over Jasmine Paolini in the first round in Tokyo.
In other round-of-16 matches on Thursday at the Pan Pacific Open, Parks defeated Kimberly Birrell 6-3, 6-1, and Leylah Fernandez defeated No. 5 Elise Mertens 6-2, 7-6 (8).
In a late match, top-ranked Elena Rybakina faced Yulina Putintseva. Both were born in Russia but represent Kazakhstan.
Second-seeded Maja Chwalinska and No. 4 Belinda Bencic pulled out of the tournament earlier with injuries. Chwalinska has an injured left thigh and Bencic has a right-ankle injury.