Naomi Osaka says she is "not far off" the form that brought her four Grand Slam titles, but admits she has thought about quitting and often ponders her future.

The 29-year-old Japanese star twice won both the US Open and Australian Open, between 2018 and 2021, during a glittering start to her career that took her to number one in the world.

She took time out of the sport in 2021 to prioritise her mental health and another 15 months away after becoming pregnant, before returning in 2023 following the birth of her daughter.

Osaka now says that she would quit tennis if her three-year-old, Shai, asked her to, despite climbing back up the world rankings and once again challenging for major titles.

"It's tough, sometimes I look towards my future and I often wonder how long I'm going to play," said Osaka, as she prepares to take part in the Pan Pacific Open in Tokyo.

"Because if my daughter did say she didn't want me to travel as much, I'm not the type of person to ignore that."

Osaka acknowledged that her mindset has changed a lot with age and the extra responsibilities that come with parenthood, saying "my daughter is my biggest priority".

"I try my best to put as much energy as I can into tennis," she said.

"I wouldn't say I'm part-timing it, but my entire day doesn't consist of that.

"If I think about it in certain ways, I'm really proud of where I am now because it's not like I can dedicate my entire time to the sport."

Osaka has battled her way back up to 19th in the world and is the seventh seed at this week's tournament, where she plays Italy's Jasmine Paolini in the opening round.

Osaka beat top seed Aryna Sabalenka on her way to the quarter-finals of Wimbledon earlier this year, after finishing runner-up in the preceding grass tournament at Bad Homburg, and also reached the last 16 of the French Open and US Open.

Osaka also made it to the semi-finals in Washington and last eight in Toronto during the North American hardcourt swing, and her run at Flushing Meadows was only ended by eventual champion Elena Rybakina.

"I genuinely don't feel like I'm that far off," she said, when considering if she can get back to winning titles.

"I think there are certain instincts that I don't want to say I lost, but maybe I forgot and I'm kind of relearning, but yeah, I don't think - I hope - I'm not far off.

"I think I built a pretty solid base and I'm just excited to see if I can continue learning and going further in tournaments."

Osaka is in the opposite side of the draw in Tokyo to Kazakhstan's world number one Rybakina, who goes into the tournament on the back of winning her fourth title of the year at the Ningbo Open in China.

The defending champion powered past Canada's Leylah Fernandez 6-2 6-2 in Sunday's final to claim a first tournament victory since last month's US Open.

Elsewhere, Daniil Medvedev successfully defended a title for the first time in his career, beating Nikoloz Basilashvili 6-7 (6-8) 6-1 6-3 in the final of the Almaty Open for his 25th men's singles crown and fourth this season.

And at the Lyon Open, the British pair of Lloyd Glasspool and Julian Cash beat France's Theo Arribage and Albano Olivetti 4-6 6-3 10-8 in the men's doubles final to record their 12th ATP title together.