TOKYO: Rio Olympic champion Monica Puig beat seventh seed Petra Kvitova 1-6, 6-4, 6-4 with a dogged display to reach the Pan Pacific Open quarterfinals on Wednesday.

Puig, who beat Germany’s Angelique Kerber in last month’s Olympic final to capture Puerto Rico’s first ever gold medal, recovered from a nightmare start in Tokyo to stun Czech Kvitova, a two-time Wimbledon champion.

“The balls felt heavy today with the roof open,” said Puig. “It took some time to adjust to the conditions but I kept fighting and that’s what got me through.”

In other matches, former world No.1 Caroline Wozniacki also advanced, the Dane toppling fourth seed Carla Suarez of Spain 7-6, 4-6, 6-4 while Japanese teenager Naomi Osaka upset Slovakia’s Dominika Cibulkova 6-2, 6-1.

Osaka, born of a Japanese mother and Haitian father and who models her game on her idol Serena Williams, insisted she paid no attention to rankings after thrashing the world No. 12.

“I honestly don’t care about that,” said the 18-year-old tournament wildcard, herself ranked 66th.

“Maybe she didn’t know much about me.”

After her upset win, Osaka revealed that her mind had wandered during the match to what she was going to eat for dinner.

Asked to pinpoint how her game has improved over a breakout season, Osaka replied cryptically: “I don’t know. To be honest, I kept thinking that I’d fancy some grilled meat.”

Arruabarrena in quarters

Spain’s Lara Arruabarrena on Wednesday advanced to the Korea Open quarterfinals after defeating US eighth seed Louisa Chirico in a near three-hour showdown.

Arruabarrena, who is the world No. 90, scored an upset victory against the 75th-ranked Chirico 4-6, 7-6 (4), 7-6 (2) in 173 minutes in Seoul.

Arruabarrena last advanced past the first round at the 2016 Ericsson Open in July, where she secured an upset win against the current No.1 Angelique Kerber in the round of 16.

The 24-year-old previously beat Chirico, 20, in the qualifying stages of the 2015 Rogers Cup.

Arruabarrena will next meet second seed Johanna Larsson from Sweden, currently the world No. 45.

Camila Giorgi of Italy also went through to the quarterfinals after beating Germany’s Mona Barthel 2-6, 6-1, 6-4.

Qualifier stunner

French qualifier Alexandre Sidorenko produced the first upset at his ‘home’ Saint Petersburg Open with a straight sets defeat of sixth seed Albert Ramos-Vinolas on Tuesday.

The Saint Petersburg-born 255th in the world won his first ever meeting with the left-handed Spaniard 7-5, 6-2 in one hour 23 minutes.

On the hard court of Saint Petersburg’s Sibur Arena the 28-year-old took the first set after 51 minutes and clinched the second set after two breaks of serve.

“I started nervously but as time went on I gained more and more confidence,” Sidorenko said.

“The first set win inspired me and in the second I was in command. I’m always happy to play in my native city and this victory matters a lot for me.”

Sidorenko will now meet Italy’s Paolo Lorenzi, who battled back from a set down to beat another qualifier Mischa Zverev of Germany 3-6, 7-6 (8/6), 6-0.

Unheralded 26-year-old Serb Dusan Lajovic saw off another Spaniard Fernando Verdasco 2-6, 6-3, 6-2 to secure his second-round spot.

Verdasco, a winner in Bucharest in April, broke twice in the opening set to take it in 32 minutes but Lajovic pulled level with a break in the sixth game of the second.

Verdasco, 32, broke early in the decider but Lajovic, 73rd in the ATP rankings, rallied to win six consecutive games, the set and the match in one hour 49 minutes.

“It was a very tough match for me as I had a lot of problems in the beginning with my backhand return,” Lajovic said.