Naomi Osaka's staggering act after Ash Barty Olympics shocker

Just hours after Ash Barty's stunning loss in the first round of the Olympics tennis event, Naomi Osaka returned to the global spotlight with a brutal victory.

Osaka powered through her opening match at the Tokyo Games on Sunday after World No.1 Barty stumbled out of the tournament after a lacklustre, error-strewn performance.

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Barty lamented a "loose and erratic" effort after she fell flat in a shock loss to unheralded Spaniard Sara Sorribes Tormo.

The World No.48 beat the World No.1 and newly crowned Wimbledon champion 6-4 6-3 in the biggest shock of the Games to date as the Australian fell apart in the blistering Tokyo heat.

Barty made a staggering 55 unforced errors to the Spaniard's 13, the Queenslander desperately out of sorts 15 days after clinching her second grand slam title.

"It was a tough day. A disappointing day. I can't lie about that," Barty told the Seven Network.

"I can't hide behind that fact that I wanted to do really well here. Today wasn't my day.

"Just loose. I knew I wanted to try to take the match on (and) it would be a fine line of not pushing too hard and not getting in the patterns I didn't want to get stuck in.

"(I was) too erratic."

Following Barty on Centre Court, Osaka then came out and trounced China's Zheng Saisai 6-1 6-4 in her first match since her shock withdrawal at the French Open in June.

Aiming to become only the fourth singles player since 1988 to win Olympic gold on home soil, Osaka admitted to having the jitters but showed no signs of pressure.

"I felt really nervous being in Japan and playing here for the first time in maybe two years, and for it to be my first Olympics," Osaka told reporters.

"It was definitely really nerve-wracking. But I am glad I was able to win. She is a very tough opponent."

Ash Barty loss opens door for Naomi Osaka gold

The four-time grand slam champion, who lit the Olympic cauldron on Friday, is widely seen as one of Japan's biggest medal contenders with all four of her major titles coming on hard courts - the same surface used at the Ariake Tennis Park.

Osaka said she was feeling refreshed having been on an extended break since May to focus on her mental health.

The World No.2 was also unbothered by the sweltering heat that has troubled other players in Tokyo.

"It feels fine for me... I love being here, and I actually really like the weather," she said.

The scorching, humid conditions had men's No.1 Novak Djokovic calling for matches to begin later in the day after his first-round victory on Saturday.

Although the schedule remained the same on Sunday, a concession was made with longer breaks at changes of ends as part of the extreme weather policy.

"It's brutal, like an Australian summer (but) I enjoy the heat and love playing out here in these conditions. Wasn't meant to be," Barty said.

It leaves Barty's medal hopes resting on the doubles, having advanced to the second round with Storm Sanders after a win on Saturday.

Her exit opens the door for a fairytale Osaka gold, but also sparked the inevitable talk that Osaka is the more deserving World No.1, which one tennis writer described as "atrocious".

with agencies

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