Seventh seed Agnieszka Radwanska of Poland beat American Coco Vandeweghe to advance to the second round of the Pan Pacific Open on Monday, but there was an early exit for Japanese wild card Naomi Osaka.
Radwanska showed the kind of form that helped her win this tournament four years ago, taking just under 90 minutes to register a 6-3, 6-3 victory in the $1,000,000 event at Ariake Tennis Forest Park in Tokyo.
The Pole had won her previous two meetings with Vandeweghe, most recently this summer in New Haven.
"We just played a few weeks ago and I knew what to expect," Radwanska told the WTA's website.
"I think it was a really good match — much closer than New Haven. There were a lot of tight games, and that long one in the second set really helped me through."
Radwanska will face the winner of an all-Ukrainian match on Tuesday between Olga Savchuk and Elina Svitolina.
Osaka was handed a straight-sets defeat by Barbora Strycova, going down 7-5, 6-2 to her Czech opponent.
Strycova will next face Spanish third seed Garbine Muguruza, who has a first-round bye.