Ashleigh Barty suffered a shock defeat to Sara Sorribes Tormo in the first round of the women’s Olympic tennis singles in Tokyo.

The world number one was the top seed and heavily favoured to mount a title challenge after winning Wimbledon recently but was humbled by the Spaniard, who won in straight sets.

Tormo raced into an early 4-1 lead in the first set and held on to snatch the opener 6-4 despite a Barty fightback.

In the second, both players struggled to hold serve before Tormo secured the crucial break at 4-3 –– closing out the match to set up a clash against France’s Fiona Ferro.

Speaking after the game, Barty admitted she had been far from her best and her play had been somewhat erratic at times.

“It was a tough day, a disappointing day. I can’t lie about that. It was just loose,” she told the Seven Network.“I knew I wanted to try and take the match on today and it was going to be a fine line of pushing too hard and not getting stuck into patterns I didn’t want to get stuck in. [I was] just too erratic today, I wasn’t able to make enough balls.”

The 25-year-old refused to blame the heat though, despite describing conditions as “brutal.”

Addressing the high temperatures, Barty said: “This is like an Australian summer for me. I quite enjoy the heat. I love playing out here in these kind of conditions, but it wasn’t meant to be today.”

Meanwhile, Barty’s rival Naomi Osaka beat China’s Zheng Saisai 6-1 6-4 to set up a round two encounter with Viktorija Golubic.

This was the Japanese star’s first game back after an extended period away from the game for mental health reasons, but the world number two looked imperious, especially on her preferred hard court surface.

As she chases a first Olympic medal on home turf, she is without question the gold medal favourite this year.