Superstar gymnast Simone Biles withdrew from the team competition in Tokyo on Tuesday with “a medical issue,” according to USA Gymnastics.

Biles walked off the floor with her trainer after competing in the vault on Tuesday. Teammate Jordan Chiles then filled in for Biles on the uneven bars.

“Simone has withdrawn from the team final competition due to a medical issue,” USA Gymnastics said in a statement.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

Biles’ teammate, MyKayla Skinner, who suffered her own heartbreak when her Olympic journey came to an end in Sunday’s qualifying round, said she was anguished at the news that Biles had bowed out.

“My heart broke for her,” Skinner told TODAY on Tuesday. “I can’t even imagine what she’s going through right now. I wish I could run down there and give her a big hug.”

The withdrawal of the 24-year-old star deals a serious blow to Team USA’s chances of defending its gold medal from the 2016 Olympics.

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Biles also entered as the heavy favorite to win gold in the individual all-around competition as well as multiple other events.

“You can never give up on hope … They can do this, I don’t know if they’ll be able to pull into first,” Skinner said. “I’m not sure; I’m hoping they can still take on the silver medal, or maybe the bronze. I guess we’ll just have to see how they do and handle this pressure.”

Biles became the first woman since 1992 to qualify for the finals in the individual vault, floor, beam and uneven bars as well as the team competition, but uncharacteristically struggled at times during the qualifying rounds.

She went off the mat following a tumbling pass in the floor exercise and took a shaky step backward in her dismount from the balance beam. She also stepped out of bounds during the vault exercise.

“It wasn’t an easy day or my best but I got through it,” Biles wrote on Instagram after the qualifying round. “I truly do feel like I have the weight of the world on my shoulders at times. I know I brush it off and make it seem like pressure doesn’t affect me but damn sometimes its hard hahaha! The Olympics is no joke! BUT I’m happy my family was able to be with me virtually, they mean the world to me!”

Biles entered the Olympics undefeated in all-around competitions at the Olympics, world and national levels since 2013.