Simone Biles stunned sports fans worldwide when Team USA announced her sudden withdrawal in Tuesday's women's gymnastics team finals in the Tokyo Olympics. The reason behind her early exit has now been revealed, with Biles withdrawing due to mental health concerns.

Simone Biles arrived in Tokyo as one of the United States' main gold medal hopefuls. She won a total of six medals in the 2016 Rio Olympics, four of which were golds. Biles was expected to add to her burgeoning medal tally in Japan as she entered the competition as the best female gymnast in the world and is widely considered the greatest of all time.

Biles stuns Team USA with sudden withdrawal

Olympic athletes are still human, though, and the pressure was just too much for Biles to handle in one of the marquee events in this year's Summer Games. Biles knew something was amiss when she posted a low score in her opening routine in the team event.

Biles was supposed to do an "Amanar" vault that requires a gymnast to execute a roundoff back handspring onto the table followed by 2 1/2 twists. Biles failed to execute that attempt as she did just 1 1/2 twists with a big leap forward after landing.

After that uncharacteristic mistake, Biles talked to U.S. team doctor Marcia Faustin and decided to head to the back while the rest of her American teammates moved on to uneven bars. Biles returned minutes later without her bar grips as she hugged and informed her teammates that her night was over.

The Americans tried their hardest to keep pace with ROC in the team final, but Biles's sudden withdrawal was just too much to overcome. Team USA's silver medal finish was still a remarkable accomplishment, especially given the unexpected events that transpired during the day.

Biles opens up about stress and pressure in the Olympics

Biles paid tribute to her teammates for their performance, saying it was best that they took over, and they are silver medalists because of it. Biles gave a motivational speech to her teammates after her sudden exit, telling them, "You guys have trained your whole entire life for this, it's fine." Biles then concluded her statement by saying, "This is your first, you go out there and kick a**, okay?"

Biles talked to TODAY's Hoda Kotb after the event and said that pressure in the Olympics had taken its toll on her. She told Kotb, "Physically, I feel good, I'm in shape but emotionally, that kind of varies on the time and moment."

Biles talked more about the stress she is currently experiencing in an interview with Olympics.com after Tuesday's event, saying, "It's been a really stressful Olympic Games as a whole."

Biles did not rule out withdrawing from the Tokyo Olympics altogether, saying she's going to take it day by day at this point. Biles is scheduled to compete in Thursday's all-around competition, where she is the defending champion.

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