The American women won silver in the women's Olympic gymnastics team final on Tuesday in Tokyo, but for three out of the four rotations, they were without superstar Simone Biles. 

After competing on vault — albeit well below her usual standards — Biles withdrew from the competition for a then-undisclosed reason. In a statement, USA Gymnastics said that she was dealing with a "medical issue."

In a post-competition interview with NBC's Andrea Joyce, Biles explained that she was working through a "mental" problem, rather than a physical one.

"We’re just dealing with a couple of things right now. So we’re just going to focus at heading into other competitions," the 24-year-old Biles said. "But I’m excited that these girls could step up to the plate as fast as they could with the switch out and I’m proud of how they did tonight."

In qualifications two days ago, Biles became the first woman since 1992 to advance to all six possible gymnastics finals (team, individual all-around, vault, beam, bars and floor), so she could potentially still compete in five more events in Tokyo. Asked what her plans are for those finals, Biles said: "We’re going to take it one day at a time and just check and see."

In Biles' stead, Suni Lee, Jordan Chiles and Grace McCallum stepped up. Chiles faced the toughest situation in having to come off the bench for two events she had initially planned to sit out: bars and beam. 

"Throughout the whole thing, I was telling myself like, 'This is for the team, I'm gonna have to do what I normally do throughout each training that I've done and show out,'" Chiles said. "And you know, at the end of the day, it was all for the team ... it was very stressful and emotional, but we're good."

"We did it for Simone," Lee added.