The host country's superstar is out of the Tokyo Olympics.
Naomi Osaka lost to former French Open finalist Marketa Vondrousova of the Czech Republic 6-1, 6-4 in the third round of the Olympic tennis tournament on Tuesday.
The second-ranked Osaka, who was born in Japan and grew up in the United States, struggled with her usually reliable groundstrokes while the left-handed Vondrousova produced a series of drop-shot winners and other crafty shots that drew her opponent out of her comfort zone.
“It's tough for her also playing in Japan and in the Olympics,” the 42nd-ranked Vondrousova said. “It's so much pressure, I cannot imagine.”
Osaka, who lit the Olympic cauldron in Friday's opening ceremony, won her opening two matches in straight sets following a two-month mental-health break. But conditions were different Tuesday with the roof closed because it was raining outside.
Shortly after the match was over, organizers said that Osaka had left the venue and would not be talking to the media.
Osaka spoke openly to reporters after her first two matches. That came after she announced in May going into the French Open that she wouldn't speak to reporters at that tournament, saying those interactions create doubts for her.
Then, after her first-round victory in Paris, she skipped the mandatory news conference.
Osaka was fined $15,000 and — surprisingly — publicly reprimanded by those in charge of Grand Slam tournaments, who said she could be suspended if she kept avoiding the media.
The next day, Osaka withdrew from Roland Garros entirely to take a mental health break, revealing she has dealt with depression.
She sat out Wimbledon, too. So the Tokyo Games marked her return to competition.
Playing Osaka for the first time, Vondrousova came out with her entire game clicking from the start and quickly ran out to a 4-0 lead in the first set as Osaka hardly had time to gather herself.
Osaka then broke Vondrousova's serve in the opening game of the second set but almost immediately handed the break back when she double-faulted to make it 2-2.
After Osaka lost her serve again to end the match by hitting a cross-court backhand wide, she shook hands with Vondrousova at the net, walked to her chair, zipped her racket up in her bag and followed Vondrousova off the court.
But it wasn't simply an off day for Osaka; it was also an outstanding performance from Vondrousova.
“I also (beat) Simona (Halep) twice, but I think now she (Osaka) is the greatest,” Vondrousova said.
“The greatest in the game, and she was also the face of the Olympics so it was tough for her, I think, to play like this."
During one point midway through the second set, Vondrousova hit an underspin, scooped forehand approach shot that landed right on the line — prompting Osaka to stare at the line for a few seconds in apparent disbelief.
Osaka had break points to take a 4-3 lead in the second but Vondrousova hit consecutive drop-shot winners to get back in the game. And then held.
About 10 minutes later, the match was over.
“I just really believed the second I stepped on the court," Vondrousova said.
“I think that that's the main thing.”
Vondrousova's quarterfinal opponent will be either Paula Badosa of Spain or Nadia Podoroska of Argentina.
In men's action, third-seeded Stefanos Tsitsipas of Greece beat Frances Tiafoe of the United States 6-3, 6-4 to reach the last 16.
And Novak Djokovic added another medal event to his program by entering the mixed doubles draw with Serbian partner Nina Stojanovic.
Tsitsipas is also entered in mixed with Maria Sakkari.