US Open champion Osaka says fame won't affect her game

US Open champion Naomi Osaka admitted Saturday she is still grappling with her newfound stardom but believes the overwhelming attention won't affect her game at the season-ending WTA Finals in Singapore.

The 21-year-old stunned 23-time Grand Slam champion Serena Williams in a controversial final at Flushing Meadows in September.

After becoming the first Japanese player to win a Grand Slam singles title, Osaka has received several lucrative endorsement deals and featured prominently in the media, including an appearance on the Ellen DeGeneres Show in the US.

Osaka said her life had changed since the US Open but vowed to remain focused on tennis.

"With the recognition part, I do feel a bit different," she told reporters in Singapore.

"Like before it was only Japan I felt like people knew me. But now like... in the airports and stuff... I just think that's (the attention) kind of funny.

"For me, I can't change who I am. I haven't really thought about changing my personality. I just focus on my matches, so I just play tennis and I leave the rest up to everyone that I trust." Since winning in New York, the world number four has fallen short in Tokyo and Beijing.

At the China Open, she required treatment to her lower back during her semi-final defeat to unseeded Anastasija Sevastova.

But Osaka has a chance to finish a memorable year on a high in Singapore, which starts on Sunday.

The rising star is the youngest player in the draw and she starts the round-robin event on Monday against American Sloane Stephens, who won the US Open in 2017.

In her WTA Finals debut, Osaka has been drawn in the tough red group alongside Stephens, Wimbledon champion Angelique Kerber and Kiki Bertens of the Netherlands, who qualified after world number one Simona Halep pulled out due to injury.

"I'm not really used to round robins. But I also think it's a really good thing, because if you happen to lose a match, it doesn't automatically mean you're out of the tournament," Osaka said.

The white group features defending WTA Finals champion Caroline Wozniacki, Czech players Petra Kvitova and Karolina Pliskova, and Ukrainian Elina Svitolina.