Japan’s Naomi Osaka was threatened with disqualification from French Open on Sunday if she persists with her controversial media boycott, the board of Grand Slam tennis tournaments said.

Osaka was fined $15,000 for skipping the news conference after her first victory at Roland Garros. Grand Slam tournaments said, “We have advised Naomi Osaka that should she continue to ignore her media obligations, she would be exposing herself to possible further code of conduct infringement consequences,” in a statement.

“As might be expected, repeat violations attract tougher sanctions including default from the tournament and the trigger of a major offense investigation that could lead to more substantial fines and future Grand Slam suspensions.”

The four-time Grand Slam title winner and sports highest-earning female athlete, Osaka refused to hold a press conference after her opening 6-4, 7-6 (7/4) victory over Romanian world number 63 Patricia Maria Tig.

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Earlier this week on the eve of the tournament, Osaka said that she would refuse to carry out any media obligations, citing mental health reasons. She likened traditional post-match inquests to “kicking people when they’re down”.

French Tennis Federation president Gilles Moreton described Osaka’s vow of silence as “a phenomenal error”. She was reminded of her obligations and the consequences of not meeting them and that rules should equally apply to all players.

The four Grand Slam events — Wimbledon, the French, Australian, and US Opens — said they had written to Osaka “to check on her well-being and offer support”.

Today, Naomi chose not to honour her contractual media commitment and therefore, Roland Garro’s referee issued her a $15,000 fine. After the match, she agreed only to a cursory on-court TV interview.

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Philippe Chatrier, the reigning US and Australian Open champion had said, “For me, playing on clay is a work in progress. Hopefully the more I play, the better I will become.”

And that was that from a player who has now strung together 15 successive Grand Slam match wins.

“There is nothing more important than ensuring no player has an unfair advantage over another, which unfortunately is the case in this situation if one player refuses to dedicate time to participate in media commitments while the others all honour their commitments,” the Grand Slam Board said, Osaka’s refusal to take in media duties puts opponents at a disadvantage.

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If Osaka was to be disqualified, it would be as sensational as Novak Djokovic’s default at last year’s US Open where the world number one was booted out for hitting a line judge with a ball.

“For me personally, I was always trying to follow the rules and be fair not only on the court but off the court as well. Now it’s up to them to decide what’s going to be,” said former two-time Wimbledon winner Petra Kvitova after her opening win.

Kei Nishikori, Osaka’s compatriot added, “It’s not good but I understand her situation. So it’s good and bad.”