U.S. gymnast Simone Biles pulls out of 2nd event, citing need to focus on mental well-being

Simone Biles will not defend her Olympic title.

The American gymnastics superstar has withdrawn from Thursday's all-around competition to focus on her mental well-being. USA Gymnastics said in a statement that the 24-year-old is opting to not compete. The organization also said Biles will be evaluated before deciding if she will participate in next week's individual events.

The decision comes a day after Biles removed herself from the team final following one rotation because she felt she wasn't mentally ready.

Jade Carey, who finished ninth in qualifying, will take Biles's place in the all-around. Carey initially did not qualify because she was the third-ranking American behind Biles and Sunisa Lee. International Gymnastics Federation rules limit countries to two athletes per event in the finals.

Biles withdrew from team competition earlier

Biles withdrew from the competition on Tuesday following one rotation — the vault — a stunning decision that opened the door for the team representing the Russian Olympic Committee (ROC) to surge to gold. Her American teammates held on for silver after the 24-year-old realized following a shaky vault she wasn't in the right headspace to compete.

"I didn't want to go into any of the other events second-guessing myself," Biles said. "So, I thought it would be better if I took a step back and let these girls go out there and do their job."

Biles says she started feeling a nervousness she couldn't explain hours prior to the competition.

"I was just like shaking, could barely nap," Biles said. "I've never felt like this going into a competition before."

Biles spent the final three rotations serving as head cheerleader while Grace McCallum, Sunisa Lee and Jordan Chiles carried on without her. The Americans — fuelled by an uneven bars routine by Lee that not even Biles could match — drew within eight-tenths of a point through three rotations. ROC, however, never wavered on floor. And they erupted when 21-year-old Angelina Melnikova's score assured them of the top spot on the podium for the first time since the Unified Team won in Barcelona in 1992.

"The impossible is possible now," Melnikova said.

Biles's teammates praised her for remaining on the competition floor, cheering them on and even helping get chalk for them ahead of their events.

"It meant a lot to us because she's the leader of our team," Lee told CBC Sports. "When your idol is out there helping you get through all of your routines, it's something that's so special that I'm going to cherish forever."

WATCH | Simone Biles praises her teammates:

In an Instagram post following the competition, Biles praised her teammates for being "incredibly brave & talented."

"I'll forever be inspired by your determination to not give up and to fight through adversity! They stepped up when I couldn't. Thanks for being there for me and having my back! Forever love y'all."

Great Britain edged Italy for bronze.

The ROC's victory came a day after the men's team edged Japan for the top spot in the men's final.

The U.S. entered the women's finals hoping to bounce back from a shaky performance in qualifying, when the Americans came in second to the ROC.

Biles posted on social media Monday that she felt the weight of the world on her shoulders. It affected her practice. It affected her confidence. And when she stepped onto the vault runway, it finally found its way to her performance, too.

"To see her kind of go out like that is very sad because this Olympic Games, I feel like, is kind of hers," Lee said.

Biles was scheduled to do an Amanar vault, which begins with a roundoff back handspring onto the table followed by 2½ twists. She seemed to change her mind in mid-air, however, doing just 1½ twists instead.

She walked off the podium and was tended to by team doctor Marcia Faustin before making her way out of the arena. Her teammates moved on to the uneven bars without her.

When Biles returned several minutes later, she hugged her teammates and took off her grips. And just like that, the greatest of all time's night was over.

WATCH | Simone Biles withdraws from gymnastics team competition: 

"It's very uncharacteristic of me," Biles said. "So it just sucks that it happens here at the Olympic Games than have it happen at any other time. But, you know, with the year that it's been, I'm really not surprised."

In a statement issued previously, USA Gymnastics did not specify the nature of Biles's medical issue, saying that she "will be assessed daily to determine medical clearance for future competitions."