Tokyo — It wasn't the ending that Naomi Osaka — nor her multitudes of fans across Japan and worldwide — had expected.

The start of the Tokyo Olympics, however, will forever be a bright memory for the tennis superstar.

Osaka herself said after lighting the Olympic cauldron during last week's opening ceremony that it was "undoubtedly the greatest athletic achievement and honor I will ever have in my life."

So maybe — just maybe — that will allow Osaka to cope with her unexpected 6-1, 6-4 loss to former French Open finalist Marketa Vondrousova of the Czech Republic in the third round of the Olympic tennis tournament on Tuesday.

Not immediately, though.

"I'm disappointed in every loss, but I feel like this one sucks more than the others," Osaka said.

As a four-time Grand Slam champion, the highest-paid female athlete in the world and the host country's poster girl for the Games, the huge expectations were hard to handle.

"I definitely feel like there was a lot of pressure for this," Osaka said. "I think it's maybe because I haven't played in the Olympics before and for the first year (it) was a bit much."

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 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.

Osaka had talked earlier this week about how "happy" she was to be playing again. 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 and anxiety.

She sat out Wimbledon, too. So the Tokyo Games marked her return to competition.

"I've taken long breaks before and I've managed to do well," said Osaka, who initially did not comment after her loss, then came back out and met with a small group of reporters. "I'm not saying that I did bad right now, but I do know that my expectations were a lot higher.

"I feel like my attitude wasn't that great because I don't really know how to cope with that pressure, so that's the best that I could have done in this situation."

The day wasn't a complete loss for Japan since Kei Nishikori, a bronze medalist in 2016, beat Marcos Giron of the United States 7-6 (5), 3-6, 6-1 to reach the last 16.

Third-seeded Stefanos Tsitsipas of Greece also defeated an American, Frances Tiafoe, 6-3, 6-4.

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, who lost to fourth-seeded Elina Svitolina of Ukraine in singles in three sets.

Svitolina's quarterfinal opponent will be Camila Giorgi of Italy, who defeated Wimbledon finalist Karolina Plisova.

Also reaching the last eight were seventh-seeded Garbiñe Muguruza of Spain, No. 9 Belinda Bencic of Switzerland and No. 13 Anastasia Sergeyevna Pavlyuchenkova of ROC.

Vondrousova's quarterfinal opponent will be Paula Badosa of Spain.

In other men's matches, eighth-seeded Diego Schwartzman of Argentina, No. 12 Karen Khachanov of ROC and Jeremy Chardy of France advanced.

In doubles, Andy Murray and British partner Joe Salisbury reached the quarterfinals.

Murray, who was the two-time defending gold medalist in singles, withdrew from that competition because of a right quad strain. He decided to play the doubles tournament to return a favor from Salisbury.

"Being in the top 10 in the world (in doubles) he could select his partner," Murray said. "I said to Joe that if he picked me to play doubles with him then I'd prioritize the doubles over the singles if I had any physical issues and that was the case."

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 settle in.

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."

Vondrousova has been benefitting from the strength of the Czech team. She's rooming in the Olympic Village with Petra Kvitova, Karolina Pliskova and Barbora Krejcikova. It's a quartet that has an accumulated seven Grand Slam final appearances, three major titles, two spells as No. 1 and one Olympic medal (bronze for Kvitova in 2016).

"I talked with (the) girls" before playing Osaka, Vondrousova said.

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."

Go for gold

Japan won its second straight Olympic softball gold medal, beating the United States 2-0 in an emotional repeat of their 2008 victory in Beijing that again left the Americans in tears.

Yukiko Ueno took a one-hitter into the sixth inning five days after her 39th birthday, and Japan snuffed out an American rally attempt with an acrobatic double play in the sixth inning.

No. 9 batter Mana Atsumi had a run-scoring infield hit in the fourth inning and Yamato Fujita lined an RBI single off Monica Abbott in the fifth in building a 2-0 lead.

Alaska gold

Seventeen-year-old Lydia Jacoby of Alaska pulled off a stunning victory in the women's 100-meter breaststroke, upsetting American teammate and defending champion Lilly King.

"I was definitely racing for a medal. I knew I had it in me," said Jacoby, who hails from the tiny town of Seward, which has a population of 2,733. "I wasn't really expecting a gold medal, so when I looked up and saw the scoreboard it was insane."

Only a handful of Alaska swimmers had even qualified for the U.S. Olympic trials. Jacoby was the first to ever make the team.

Streak snapped

The streak of 12 straight gold medals for the U.S. men in the individual backstroke ended when a pair of Russians beat out defending Olympic champion Ryan Murphy in the 100-meter race.

Evgeny Rylov won the gold medal in 51.98 and teammate Kliment Kolesnikov took the silver in 52.00. Murphy settled for the bronze in 52.19.

It was the first backstroke defeat for the U.S. men at the Olympics since the 1992 Barcelona Games.

They won 12 straight golds over the past six Olympics, including Murphy's sweep of the 100 and 200 back at the 2016 Rio de Janeiro Games.

"Winning an Olympic gold medal means you're the best in the world," Murphy said. "Being third in the world is no slouch."

Moving on

The United States made it through to the quarterfinals of the women's Olympic soccer competition after a 0-0 draw with Australia.

The Americans are looking to win a fifth Olympic gold medal in Tokyo. They are also vying to become the first team to win at the Olympics following a World Cup title.

But they've made it hard on themselves at the Tokyo Games. The U.S. team lost to Sweden 3-0 in its opening match — snapping a 44-game unbeaten streak — before rebounding with a 6-1 victory over New Zealand.

Historic first

Flora Duffy has won the Olympic women's triathlon, earning Bermuda's first gold medal ever and first medal of any kind since 1976.

Duffy is a two-time former world triathlon series champion. She's competing in her fourth Olympics and is one of just two athletes representing Bermuda in Tokyo.

The start of the race was delayed 15 minutes because of storm conditions around Tokyo Bay. Duffy pumped her arms over her head as she finished the swimming, cycling and running course in 1 hour, 55:36 minutes.

Struggling champs

The expected Olympic showdown between the top two women's volleyball teams in the world turned out to be a one-sided affair.

The U.S. women swept defending gold medalist China 29-27, 25-22, 25-21 in a pool-play match that left the Americans at the top of Pool B and the Chinese seeking to win their first set of the tournament after two straight sweeps to open the Games.

China was also swept by Turkey in the opener but showed five years ago in Rio de Janeiro how little the pool-play matches can mean after losing three of five of them before rallying to win gold.