But moments before pulling off the most clutch performance of her gymnastics career, Chiles didn't really believe what was transpiring around her.
"I was shocked. I was overwhelmed," Chiles told NBC's Maria Taylor. "After she did her vault, Cecile [Landi] came over and was like 'Jordan put your grips on.' I was in so much shock that I didn't know if she was being serious or not. So I was just putting my grips on like 'What am I doing?'"
"And then she told me and I was like okay, this is where I have to actually pull myself together and actually do this," she added.
So she did.
Advertisement
Chiles acted as the first emergency substitute for Biles during the second rotation of the final, taking on far from her strongest event in the uneven bars. Just a few days after a shaky showing in the qualification event, she posted a 14.166 - relatively low by American standards, but higher than the vast majority of the field.
She nailed her surrogate role again in the following rotation. Chiles' 13.433 on the balance beam was, as expected, the lowest of the American contingent. But it was good enough to best Russians Vladislava Urazova and Angelina Melnikova - who went on to win gold with the Russian Olympic Committee - and help Team USA stay afloat.
Both performances were remarkable considering the last-second nature of her preparations.
"I wasn't supposed to be doing bars and beams, so I didn't know what was going to happen - if she was going to continue or if she wasn't," Chiles said.
"So in that moment, we're all kind of like, panicking," she added. "But at the same time, we knew we had to put something together and calm ourselves down because we had a job to do."
Advertisement
Alongside teammates Sunisa Lee and Grace McCallan, Chiles strung together a series of sensational performances to lead Team USA to a second-place finish.
Chiles' and McCallum's runs in Tokyo came to an end Tuesday, but Biles and Lee are set to return to the gym on Thursday for the individual all-around final.
Should Biles choose to participate, the 24-year-old will look to defend her individual all-around title from 2016.
{{}}
NewsletterSIMPLY PUT - where we join the dots to inform and inspire you. Sign up for a weekly brief collating many news items into one untangled thought delivered straight to your mailbox.