TOKYO, Japan (AFP) — US gymnastics superstar, Simone Biles, sent shock waves through the Olympics yesterday, tearfully citing concerns for her mental health after a dramatic withdrawal mid-competition during the women’s team final.

The 24-year-old four-time Olympic gold medallist — one of the faces of the Tokyo Games — got off to a shaky start at the Ariake Gymnastics Centre with a lacklustre opening vault.

Stunned onlookers watched as Biles was led off the competition floor before returning wearing a tracksuit. Soon afterwards, USA Gymnastics confirmed she would sit out the remainder of the final with an unspecified medical issue.

Speaking to reporters after the final — eventually won by Russia’s team — Biles said concerns for her mental well-being prompted her decision to withdraw.

“At the end of the day, I have to do what’s right for me and focus on my mental health and not jeopardise my health and my well-being,” she said.

“I just think mental health is more prevalent now in sports and it’s not just like we have to set everything aside, we also have to focus on ourselves.

“Because at the end of the day we’re human, too, so we have to protect our mind and our body rather than just go out there and do what the world wants us to do.”

If Biles fails to recover in time for Thursday’s individual all-around competition, it would mark a stunning turn of events at a Games which she had been strongly expected to dominate.

Biles later began crying as she revealed a loss of confidence in her abilities.

“I just don’t trust myself as much as I used to,” she said, flanked by her US teammates. “I feel like I am also not having as much fun. That just hurts my heart that doing what I love has been taken.”

Another face of the Games — Japan tennis star Naomi Osaka — also fell by the wayside yesterday after losing 6-1, 6-4 to Marketa Vondrousova following an error-strewn performance.

The 23-year-old Osaka had not played since May, when she walked out of the French Open saying media commitments were harming her mental health.

The second seed was bitterly disappointed at missing out on a chance of Olympic gold, especially after the early exit of world number one Ashleigh Barty.

“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, who lit the Olympic cauldron at last Friday’s opening ceremony.