Naomi Osaka is out of the tennis tournament.

Naomi Osaka, the Japanese superstar who lit the caldron during the Olympic opening ceremony, was eliminated in the third round of the women’s singles tennis tournament on Tuesday in straight sets.

Osaka lost, 6-1, 6-4, to Marketa Vondrousova of the Czech Republic in barely over one hour in a stunning upset of the host country’s biggest sports celebrity. The defeat ended Osaka’s run at the Tokyo Games.

Osaka breezed through her first two matches, the first competition she has faced since dropping out of the French Open in June to deal with mental health issues.

On Tuesday, however, Osaka struggled from the outset. For long stretches of the first set, Osaka battled to keep the ball in play. She committed 20 errors in the set, 14 of them unforced, and while she did not double fault, she also could not rely on her serve to take control of the match the way she usually does.

The loss stunned the handful of people in attendance at Ariake Tennis Center, where a phalanx of Japanese photographers lined the court. Osaka, the No. 2 player in the world, was a favorite to win the tournament on home soil, especially after Ashleigh Barty, the world No. 1, was eliminated in the first round and other top players lost in Round 2.

Osaka, who dropped out of the French Open over a dispute with tournament officials over whether she should have to attend mandatory news conferences following her matches, made a brief visit to the players lounge after the match then left the grounds before returning later to speak with the press.

Because Osaka lit the Olympic cauldron late Friday night in the climax of the opening ceremony of the Tokyo Games, her opening match was moved from Saturday morning to Sunday. As a result, Osaka was playing for a third consecutive day.

Osaka said the pressure of being the face of the event probably played a role in the loss but did not want to use it as an excuse.

“I should be used to it by now, but the scale of everything is a bit hard because of the break that I took,” she said. “I’m glad I did not lose in the first round, at least.”

Osaka battled to find her rhythm in the second set, which was much tighter than the first. She nearly matched Vondrousova on points and even managed to break Vondrousova’s serve, but the young Czech played with a cool beyond her 22 years, given the magnitude of the moment. She neutralized Osaka’s power with a series of spins and slices that never allowed Osaka to get comfortable.

“This is one of the biggest matches of my career,” Vondrousova said. “Naomi is the greatest now. She was also the face of the Olympics, so it was also tough for her to play like this.”

Vondrousova said she benefited from the timing and location of the match. She and Osaka played second on center court and with a roof in place on Tuesday they did not have to worry about weather delays.

When it was over she and Osaka had a brief exchange at the net, with Osaka telling her “good match” and Vondrousova thanking her for the compliment.

“I am really sorry but I am so happy with my game today,” Vondrousova said of knocking off the biggest star of the Olympics for Japan. “She has a lot of pressure playing in Japan and at the Olympics. I knew she was going to fight to the end. The end was very tight. It could have gone both ways. It’s so much pressure I can’t imagine.”

The Olympic tournament has been a tough nut to crack for even some of the game’s greatest players. It requires winning six matches in just eight days. Roger Federer has never won the gold medal.

Osaka arrived after causing upheaval in the tennis world, and intensified the discussion around athletes and mental health, when she withdrew from the French Open and skipped Wimbledon as well after her refusal to endure what she called the stress of mandatory news conferences at tennis events, especially at Grand Slam tournaments.

She revealed that she has struggled with depression since 2018, and said she is uncomfortable in the sometimes adversarial public setting of news conferences. She quit the tournament after organizers threatened to disqualify her if she did not meet her press obligations.

During the fracas, Osaka’s sister, Mari, a recently retired professional tennis player, said in a Reddit post that she later deleted that Osaka’s decision to skip news conferences was part of a strategy to avoid discussing her difficulties playing on clay, the surface used at the French Open.

To the public, it was unclear for a while when Osaka would play again, even with the Olympics coming. Few knew that she had been asked in March to light the Olympic flame and skipping the tournament was extremely unlikely given the magnitude of that honor.

So in mid-June she announced she would skip Wimbledon, which is contested on grass, but would return to competition at the Tokyo Games.

She was born in Japan and chose to represent the country in international competition in 2019. Osaka’s mother is Japanese and her father is Haitian. She was raised largely in the United States. The Olympic tournament is also played on a hard court, the surface on which Osaka has had the most success.

On Friday night, joined a short list of illustrious Olympic flame lighters, including Muhammad Ali and Wayne Gretzky.

Two days later she was still absorbing the experience and adjusting to life as the face of Olympic stardom.

“I feel a little bit out of my body right now,” Osaka said on Sunday, minutes after winning her first-round match.

She was uncertain about her next move. “I’m sort of a person that wings a lot of things. That is either a really good thing or a really bad thing,” she said.

Osaka will now likely head to North America for the hard court swing of the professional tennis tour that climaxes with the United States Open in late summer. She is the defending U.S. Open champion and will be looking for her fifth Grand Slam singles title.

She said she remains happy to be at the Olympics in Tokyo, despite the loss. “All in all really happy with my first Olympic experience.”