Naomi Osaka’s return to the French Open was triumphant as she won her first-round match over Patricia Maria Tig on Sunday in straight sets. But Osaka did not emerge unscathed from the tournament’s opening day.

She was fined $15,000 by the French Open tournament referee for declining to appear at a mandatory postmatch news conference and warned that she risked stronger penalties, including default from the tournament, if she continued not to fulfill her media obligations.

That surprisingly stern warning was delivered in a statement signed by the leaders of the four Grand Slam tournaments: Gilles Moretton, the new president of the French Tennis Federation; Mike McNulty, the new head of the U.S. Tennis Association; Jayne Hrdlicka, the head of Tennis Australia; and Ian Hewitt, chairman of the All England Club, which runs Wimbledon.