Naomi Osaka created history Saturday as she became the first Japanese tennis player to win a singles Grand Slam title, but her win over Serena Williams in the 2018 US Open women’s singles final was marred in controversy.

In what was supposed to be the 20-year-old’s greatest moment in her career turned out be a day that was all about the war of words between the veteran 23-time women’s singles Grand Slam champion and the referee.

Osaka was booed by a partisan New York crowd despite being the deserved champion, after Williams was handed a game penalty by the chair umpire for three code violations. The 2018 women’s singles final will always be remembered in tennis history, but it will not only be because of the Japanese youngster’s greatest triumph in her relatively short career.

However, if we take away all the controversy and the furor surrounding Williams – in the heart of the matter lies a truly great story about the coming of age of a young Japanese star, who is being tipped to go on and conquer the tennis world on and off the court.

According to Forbes, Osaka is on her way to super stardom after her win against Williams at the US Open. The report claimed she was well on her way to replacing the American tennis legend, who is also the Japanese youngster’s idol, as the highest earning female athlete.

It was estimated her off-court earnings are likely to soar in the next couple of years from $1.5 million to $15 million. And it started with her $3.8 million prize money that she won by claiming the title at Flushing Meadows on Saturday.

Osaka’s current list of endorsement’s include Adidas, Yonex, Nissin and Wowow. The Japanese star’s contract with Adidas expires at the end of 2018 and her agent Stuart Duguid confirmed they are in talks with all the major sports apparel manufacturers, and there is likely to be a lucrative deal at the end of all the negotiations.

Osaka’s compatriot Kei Nishikori is also managed by the same agency – IMG – and Duguid admitted the multi-cultural background she has will aid in gaining more global acceptance. The same agency also handles the Japanese star’s compatriot Kei Nishikori and Osaka’s agent revealed they already have a blue print in place to make her one of the top earners off the court.

“We were already sort of managing her at IMG as one of our star female clients just based on her game, the way she looks on court,” Duguid said, as per the Daily Mail. “She’s from Japan with a multicultural background from Haiti and the United States, so she has the full package. She is very honest and down to earth and people are relating to that. She’s going to have a very successful career on and off the court.”

“We manage Kei so we know how strong that market is for endorsements, the blueprint was there,” Osaka’s agent added. “There’s a lot of companies for whom Kei is the male and they are looking for a female, so it couldn’t be better timing. Her clothing deal is up at the end of the year so we are in discussions with pretty much everyone on that.”