OSAKA — Russia's Anastasia Pavlyuchenkova stunned second seed Kiki Bertens 6-1, 7-5 to reach the Pan Pacific Open quarterfinals in Osaka on Thursday, while American Sloane Stephens suffered another early exit.

World No. 8 Bertens made a slow start and fell 4-0 behind in the opening set after serving five double faults in two games.

The Dutchwoman recovered well to share the opening four games with Pavlyuchenkova but dropped her serve in the fifth, failing to keep up with her unseeded opponent's devastating backhands.

Pavlyuchenkova converted another break point to clinch her third victory over Bertens over the last 12 months, and set up a quarterfinal date with in-form Japanese wildcard Misaki Doi.

Third seed Stephens, who has not reached a quarterfinal since the French Open in May, was outplayed in a 6-0, 6-3 defeat by Italian Camila Giorgi.

Despite landing just 38% of her first serves in the match, unseeded Giorgi made her opportunities count when she got into play and went on to win the first eight games.

The Italian number one finished with 23 winners to 21 unforced errors to book her third quarter-final appearance in her last six events, where she will face Belgian Elise Mertens.

"It was a good match for sure and I was able to play my game, show off my attacking style and be consistent," said Giorgi.

"I need to concentrate on myself and keep going. I focus on my own game but I'm looking forward to the match (against Mertens)."

Age not an obstacle to Serena's

pursuit of 24th major: Mouratoglou

Serena Williams is getting faster and fitter in her hunt for an elusive 24th Grand Slam title and the 37-year-old still has time on time on her side despite missed opportunities, the American's coach, Patrick Mouratoglou, has said.

Williams suffered her fourth consecutive defeat in a Grand Slam final at the US Open earlier this month, as she again came agonizingly close to Australian Margaret Court's all-time record of 24 majors before falling in straight sets.

Williams has not won a set in any of the four Grand Slam finals she has reached since returning from maternity leave in September 2017. At Flushing Meadows, she fell to a first-time Grand Slam finalist in Canadian teenager Bianca Andreescu.

Williams may not need statistics to prove her standing in the game but Mouratoglou is confident she has plenty of gas in the tank to continue her pursuit next season.

"I think time is working for her," Mouratoglou told Sky Sports. "I think she was much better at the US Open than she was at Wimbledon, and Wimbledon (was) better than Roland Garros.

"She is getting back in shape, and the more in shape she will be, the more dangerous she will be. I think she has started to play really good tennis."

Mouratoglou said Williams must play without the pressure of having to solidify her place in tennis history.

"This is the highest pressure anyone can have in life, and on the other side of the court she plays girls who have zero pressure because it is their first final," he said.

"At some point, she will figure out how to deal with that." — Agencies