Naomi Osaka crashes out of Olympics after shock straight sets loss

The second seed was broken twice more as 2019 French Open runner-up Vondrousova raced away with the first set

Japanese tennis star Naomi Osaka's dreams of home Olympic gold were crushed by a 6-1, 6-4 defeat to Marketa Vondrousova Tuesday as her return to action came to an abrupt end.

Osaka, who lit the Olympic cauldron and was one of the faces of the Games, struggled in an error-strewn display that blew the draw wide open after the earlier exits of world number one Ashleigh Barty and third seed Aryna Sabalenka.

"How disappointed am I? I mean, I'm disappointed in every loss, but I feel like this one sucks more than the others," said the four-time Grand Slam-winner.

Asked what went wrong, she replied: "Everything -- if you watch the match then you would probably see. I feel like there's a lot of things that I counted on that I couldn't rely on today."

The third-round defeat follows a turbulent few months for Osaka, who abandoned her French Open campaign in May after refusing to attend press conferences, citing the need to preserve her mental health.

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Osaka also skipped Wimbledon, saying she had been battling depression and anxiety, before returning in Tokyo for her first Olympics including her starring role at the opening ceremony.

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

After looking assured in the first two rounds after her eight-week hiatus, Osaka made a dreadful start under the centre court roof at a rain-hit Ariake Tennis Park and never recovered.

"I've taken long breaks before and I've managed to do well. I'm not saying that I did bad right now, but I do know that my expectations were a lot higher," she said.

"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."

Osaka dropped serve in the opening game and was broken twice more as the 42nd-ranked Vondrousova raced away with the first set.

The second seed broke in the second set but relinquished the early advantage with a double fault that allowed Vondrousova to level at two games apiece.

The 23-year-old grappled with inconsistency, and even when given a sniff of regaining the initiative she had no response to Vondrousova's array of crafty drop shots.

Osaka saved two match points as she served to stay alive at 4-5 but Vondrousova converted at the third time of asking as the Japanese superstar smacked a backhand wide.

Vondrousova will go on to face Spain's Paula Badosa or Nadia Podoroska of Argentina in the quarter-finals.

"Of course it's one of the biggest wins of my career," said Vondrousova, the 2019 French Open runner-up.

"Naomi is a great player, she has so many Grand Slams, so I knew it would be a tough match. I'm very happy with my play.

"I played amazingly in the first set, and then the second set was really tough. I'm just happy to be through."

Ukrainian fourth seed Elina Svitolina is the highest-ranked women's player remaining in Tokyo.

Earlier Stefanos Tsitsipas advanced to the men's third round as he avenged last month's Wimbledon loss to Frances Tiafoe.

The Greek third seed downed American Tiafoe 6-3, 6-4 in the opening match of the day as all play on outside courts was delayed an hour by morning drizzle.

Tsitsipas, who is also entered in mixed doubles with Maria Sakkari, will play France's Ugo Humbert or Miomir Kecmanovic of Serbia for a spot in the quarter-finals.

Having lost to Tiafoe in the opening round at Wimbledon, Tsitsipas ensured there was no repeat as a single break in each set enabled him to wrap up victory in 77 minutes.