Naomi Osaka has suggested the weight of expectation proved too much for her as she suffered a shock straight-sets defeat to Markéta Vondroušová of the Czech Republic at the Tokyo 2020 Olympics here.

The Japanese star produced a disappointing showing at the Ariake Tennis Park as she slumped to a 6-1, 6-4 loss to the world number 42.

Osaka has been the poster girl of the Games and was chosen to light the Cauldron at the Opening Ceremony on July 23.

The 23-year-old, who was making her first tournament appearance since withdrawing from the French Open in late May, came through her first-round encounter, beating Viktorija Golubic of Switzerland.

But home hopes of a gold medal are over as Osaka's serve was broken five times in a sorry defeat.

"For me, I am really glad to be here," said Osaka, who was making her Olympic debut.

"I am sad that I lost of course, but all in all really happy with my first Olympic experience."

Asked whether the extra pressure played a role in her defeat, Osaka said: "I mean yes and no.

"I feel like I should be used to it by now.

"But at the same time, the scale of everything has been a bit hard because of the break that I took.

"I am glad I didn’t lose in the first round at least."

Osaka pulled out of the recent French Open amid the fallout from her decision not to attend press conferences in order to protect her mental health.

She was warned by Grand Slam organisers that she faced expulsion from the French Open and future majors if she continued her boycott.

Since then, Osaka withdrew from Wimbledon before ending a two-month hiatus from competitive action at her home Olympics.

The world number two claimed her fourth major title when she won the US Open last year.

The Grand Slam is due to be held from August 30 to September 12.

When quizzed on what her plans were prior to the US Open, Osaka added: "My plans? Not really.

"For me, I am a person who wins a lot of things.

"That is either a really good thing or a really bad thing."

Sir Andy Murray, a two-time Olympic singles champion and Britain's flagbearer at Rio 2016, also gave his thoughts on Osaka’s early exit and believes the pressure-cooker environment of competition can benefit athletes.

"It was a bit of a surprise, but she has not played much recently," said Sir Andy.

"It’s not easy out there.

"I think you learn to deal with it [pressure].

"Maybe not for everyone, but for me, I like being under pressure.

"I like feeling nervous as it helps you concentrate better.

"Ultimately, it helps you perform better.

"Maybe the 45 minutes or hour before each match it is a little bit more difficult because you are doubting things and overthinking things a little bit more.

"But once you get out there and start hitting balls you want to feel that pressure.

"I helps you perform better and, generally, in most pressured situations you see the best performances from athletes as they are at their most focused."