TOKYO (AP) — Defending champion Agnieszka Radwanska defeated Rio Olympics gold medallist Monica Puig on Friday to set up a semifinal showdown with Caroline Wozniacki at the Toray Pan Pacific Open in Tokyo.

Second-seeded Radwanska, of Poland, smashed eight aces in overpowering the Puerto Rican 6-2 6-3.

"In this level of match you have to play well to win by that kind of score," said Radwanska, who also won this tournament in 2011.

"I knew Monica was in great form, winning the gold, but you just have to go on court and play your game. I was serving great today and that helped me a lot."

Wozniacki appears back near her best after a succession of ankle, knee and bicep injuries; reaching the U.S. Open semifinals and continuing that form here.

She beat Polish qualifier Magda Linette 6-4, 6-3. Wozniacki won 79 per cent of points on her first serve, including 90 per cent in the first set.

She holds an 8-4 head-to-head advantage against Radwanska.

"With Caroline, we've played so many matches everywhere on every surface, it's always a great challenge against her," Radwanska said. "For me she's still a top-10 player, even though her ranking dropped a bit. Hopefully I can serve just as well against her tomorrow."

Friday's other quarter finals see Belarussian qualifier Aliaksandra Sasnovich tackle Japanese wild card Naomi Osaka, while top-seeded Garbine Muguruza, of Spain, faces eighth-seeded Anastasia Pavlyuchenkova, of Russia.