We're used to perfection from Simone Biles but the American superstar sparked concerns on Tuesday night when she pulled out just minutes into the women's team gymnastics final in Tokyo.

The USA started on the vault – the place Biles has gone where nobody ever has before with the incredible Yurchenko double pike – but the four-time gold medallist baulked on her first attempt.

The bizarre incident meant she only completed 1.5 rotations instead of 2.5 and failed to stick the landing. Biles was clearly irked and grimaced on her way back, earning a 13.766 — the lowest score of all six American and ROC (Russian) competitors.

USA Gymnastics later confirmed Biles would not play any further part in the final.

Simone Biles, of the United States, watches gymnasts perform after pulling out of the Tokyo Olympics. (Photo / AP)

"Simone has withdrawn from the team final competition due to a medical issue," a statement said. "She will be assessed daily to determine medical clearance for future competitions.

"Thinking of you, Simone!"

America dealt with her exit admirably though. Jordan Chiles, Grace McCallum and Sunisa Lee fought through adversity to win a memorable silver medal, behind Russia and ahead of Great Britain.

In a team event, three members compete on each apparatus, and one is a reserve. That's why America was able to continue and secure second place despite being a woman down.

Speaking after the event, Biles said she did not know where she was in the air on her first vault and explained she had been "fighting all those demons" inside her head.

She pulled out because she did not want to jeopardise her team's chances of winning a medal.

Simone Biles, of the United States, walks after performing on the vault during the artistic gymnastics women's final at the 2020 Tokyo Olympics. (Photo / AP)

"It's just me in my head," she said. "I have to focus on my mental health and not jeopardise my health and wellbeing.

"We have to protect our body and our mind.

"It's very unfortunate this has to happen at this stage ... it just sucks when you're fighting with your own head."

"Tonight they [her teammates] get a gold medal from me for fighting."

Speaking to NBC, Biles added: "Physically, I feel good, I'm in shape. Emotionally, that kind of varies on the time and moment.

"Coming here to the Olympics and being the head star isn't an easy feat, so we're just trying to take it one day at a time and we'll see."

Biles said she will wait and see before deciding whether she will compete in her individual event.

World in shock over Biles drama

Nobody could quite believe what they'd seen from the undisputed queen of gymnastics, who has done things in the sport nobody thought possible.

American Olympics reporter Callie Caplan said Biles "looked near tears as she walked off the podium" following her first vault.

"Simone Biles got lost in the air during her last warm-up vault and bailed out of the Amanar early. She just did the same during competition, completing 1.5 twists instead of 2.5," Caplan tweeted.

Simone Biles, of the United States, enters the court for the artistic gymnastics women's final at the 2020Tokyo Olympics. (Photo / AP)

Shelia O'Connor added: "Did … did Simone Biles just bail out of her vault?" with a shocked hands-on-face emoji.

US sports columnist Nancy Armour said: "OMG. Simone bailed out of the Amanar, does a 1.5. Nearly lands it on her knees. And looks as if she's about to cry as she comes off the podium, Cecile immediately goes and puts arm around her."

American TV presenter Hoda Kotb said "the place was just stunned" at the unexpected development.

The plot thickened when Biles soon walked off the competition floor with a team trainer, sparking speculation she'd suffered an injury.

Her teammates walked over to the uneven bars and were forced to compete without her. Chiles was supposed to sit out the bars portion of the night but had to scramble to take part because of Biles' absence.

Simone Biles, of the United States, dismounts from the vault during the artistic gymnastics women's final at the 2020 Tokyo Olympics. (Photo / AP)

Before moving on to the beam, USA Gymnastics confirmed Biles had withdrawn from the competition.

In the final stages of the bars, Biles returned to the floor but had put her white team tracksuit on because she was done for the night. She walked with the team around to the beam and supported her comrades as they tried to claw their way up the leaderboard.

Just because Biles was out of action it didn't mean she wasn't going to contribute. She cheered louder than anyone as she encouraged Team USA to power on towards a medal.

The rest of the team's mood wasn't dampened as they rose to the challenge. They hugged Biles and the quartet engaged in animated chats, looking like they were having the time of their lives.

Coach Cecile Landi also showed her star pupil plenty of love, as did those members of the media allowed in the stands.

There were awesome scenes at the end of the night as Biles celebrated on the podium with her teammates.