PARIS — 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 Rémy Azémar, 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 United States Tennis Association; Jayne Hrdlicka, the head of Tennis Australia; and Ian Hewitt, chairman of the All England Club, which runs Wimbledon. The Grand Slam events' leaders also emphasized that repeat violations by Osaka could lead to "more substantial fines and future Grand Slam suspensions."Osaka, a four-time major singles champion who is one of the sport's biggest stars, is now faced with a choice. Before the French Open began, she announced that she would not do "any press" during the tournament, citing the need to preserve her "mental health" by avoiding repetitive and potentially negative questions from journalists. But if the intent was to limit distractions and find inner calm, she now faces a potentially bigger concern in Paris if she continues to abstain from news conferences."It's developed into a power struggle," said Chris Evert, an 18-time Grand Slam singles champion who is covering the French Open as an analyst for Eurosport. "Press conferences are crucial to Grand Slams to get the players' perspective of their match, and it's a collective responsibility for players to continue to grow the sport. I think we've lost sight of the early days, the '70s, when there was no women's tour, and that generation talked endlessly to the press to promote the sport and themselves. The players today are making a tremendous amount of money, and there are trade-offs."The Grand Slam leaders expressed frustration with Osaka's lack of engagement with tennis officials, explaining in their statement that the French Open management team had "tried unsuccessfully to speak with her to check on her well-being, understand the specifics of her issue and what might be done to address it on site."