Simone Biles will compete in Tuesday's beam final.
The 24-year-old will take up her final chance of an individual medal at an Olympics where she has withdrawn from four other finals.
Biles has not competed since last week's team final, where she performed on vault but no other apparatus. She then bowed out completely as she wanted to protect her mental health.
The pre-Games favourite, a four-time Olympic champion, has been suffering with the 'twisties', which gymnasts describe as a kind of mental block. But some fans worried that the media furore over her decision to pull out of the games influenced her decision to compete. Many were concerned that Biles was not fully ready.
"I really hope she didn’t feel pressured to return because white men couldn’t mind their own got dam business," one person wrote online.
"Simone…DON'T LET THEM BULLY YOU INTO THIS!!! If you don’t feel like competing, then don’t do it," a second added.
"God forbid but if she gets injured during this, all those calling her a quitter better shut up," a third commented.
One of Biles' biggest critics has been journalist Piers Morgan.
The former Good Morning Britain host took to social media to declare that it was a “joke” that the decorated US Olympic gymnast withdrew from the women’s team final for mental health reasons.
Ms Biles is the most successful US gymnast of all time.
But Biles admitted that the pressure of being the world’s pre-eminent gymnast was causing her mental health to deteriorate, leaving her worried she’d leave the Games “on a stretcher.”
“I don’t trust myself as much anymore. Maybe it’s getting older. There were a couple of days when everybody tweets you and you feel the weight of the world,” she said of the decision.
"We’re not just athletes. We’re people at the end of the day and sometimes you just have to step back. I didn’t want to go out and do something stupid and get hurt. I feel like a lot of athletes speaking up has really helped.”
Biles decision caused much annoyance and anger to Morgan, who suggested she wasn’t being sincere and was merely upset over a “poor performance.”
“Are ‘mental health issues’ now the go-to excuse for any poor performance in elite sport? What a joke,” Morgan wrote on Twitter. “Just admit you did badly, made mistakes, and will strive to do better next time. Kids need strong role models not this nonsense.”
The Editor At Large of the Daily Mail even wrote a scathing article about Biles' withdrawal from the 2021 Olympics.