Naomi Osaka raised her game when she needed to, and it landed her a spot in the semifinals of the Pan Pacific Open.

The U.S. Open champion, who upset Serena Williams in the final in New York this month, won her ninth straight match Friday, beating Barbora Strycova 6-3, 6-4.

"This was my third time playing her, and each time it was very close, so I knew she was very good," said the third-seeded Osaka, the first Japanese player to win a Grand Slam singles title.

Osaka will next face Camila Giorgi, who advanced after Victoria Azarenka retired from their match with a gastrointestinal illness in the first set. Giorgi was leading 5-3 when the match ended.

The 20-year-old Osaka converted all three of her break points and won 80 percent of points on her first serve. She hit 26 winners and had an equal number of unforced errors.

"I feel like I adjusted," Osaka said. "I knew that I wasn't playing that great today, but I still adjusted and I managed to win. I never know why certain things aren't working, but I feel like it's my job to make sure that I do the best that I can in that situation."

Osaka broke the eighth-seeded Strycova to take a 3-1 lead in the first set but was soon broken back. Leading 4-3, that's when Osaka took control. She immediately earned two break points, and Strycova double-faulted on the first one to put Osaka ahead 5-3.

In the second set, double-faults again cost Strycova, who was broken at 2-2.

Osaka has been in the spotlight both on and off the court since she arrived back in Japan following her victory in New York. Friday's match at Tachikawa Arena was sold old and Osaka's progress up the rankings has been the focus of Japanese talk shows.

She has received congratulatory messages from Japanese Prime Minister Shinzo Abe and attended the ongoing sumo tournament in Tokyo.

Also Friday, fourth-seeded Karolina Pliskova defeated Alison Riske 6-1, 6-7 (5), 7-6 (4). She will next play Donna Vekic, who beat second-seeded Caroline Garcia 6-3, 6-4.

 

Alexandrova beats top-seeded Ostapenko at Korea Open

Ekaterina Alexandrova broke top-seeded Jelena Ostapenko's serve five times Friday to beat the defending champion 6-3, 6-2 in a rain-delayed match at the Korea Open.

Ostapenko, the 2017 French Open champion, had reached the quarterfinals or better at six tournaments this year, including the Wimbledon semifinals. Alexandrova came into the match with a 1-7 career record in round-of-16 matches at WTA-level events.

The postponement from Thursday meant Alexandrova had to play her quarterfinal match later Friday against sixth-seeded Hsieh Su-wei.

Hsieh has won seven straight matches since winning last week's Japan Women's Open.

In other quarterfinal matches, second-seeded Kiki Bertens beat Evgeniya Rodina 3-6, 6-3, 6-0 and AjlaTomljanovic defeated Mandy Minella 6-2, 4-6, 7-5.

 

Thiem, Wawrinka reach St. Petersburg semifinals

Top-seeded Dominic Thiem and fit-again Stan Wawrinka won their quarterfinal matches at the St. Petersburg Open on Friday.

Austrian player Thiem came through a tough encounter against Daniil Medvedev of Russia, firing 10 aces on his way to a 6-2, 3-6, 7-6 (2) victory.

His reward is a semifinal with Roberto Bautista Agut of Spain, who won 7-6 (0), 6-3 against Marco Cecchinato.

Experienced Swiss Wawrinka, aiming for his first title since sustaining a severe knee injury last year, next plays Martin Klizan of Slovakia after beating last year's St. Petersburg champion Damir Dzumhur 6-3, 6-4.