TOKYO — Naomi Osaka used a powerful forehand and a matching serve to win the US Open against Serena Williams. Off the court — on the marketing front — experts say she could have the same potential as Williams, and maybe more.

"It's very, very rare to find a Japanese-born female athlete who appeals to an international audience," said Bob Dorfman, a sports marketing expert and creative director at Baker Street Advertising in San Francisco, California.

Serena Williams topped the Forbes list of the highest-earning female athletes this year at $18 million, almost all endorsements.

Experts say Osaka could be the right woman in the right sport at the right time with the draw to overtake her.

"What's more, tennis, especially women's tennis, is a sport that lends itself to a broad variety of sponsors: sporting goods, health and beauty, fashion, lifestyle, travel, personal care, you name it," Dorfman said. "And the sport's international following brings with it a large, loyal and affluent fan base. All the more reason why so many companies are lining up to sign her up." The big question is: Can she keep this up? Much has happened very quickly for her, notes former tennis star Chris Evert.

"You know, it's going to be life-changing for her and very, very important," Evert said. "From what I see, she is very humble and from what I see, her parents are very humble people. Hopefully they won't go Hollywood on us. We don't want that to happen." Osaka's multicultural background — Japan-born but raised in the US by a Haitian-American father and a Japanese mother — adds to her wide appeal, endearing her to fans in Japan and elsewhere.