Simone Biles' participation in the rest of the Tokyo Olympics was plunged into uncertainty on Tuesday after she was dramatically withdrawn from the team final with a "medical issue".
The American gymnastics superstar exited the final after a lacklustre opening vault and briefly left the competition floor, before returning to join her teammates.
But the US team replaced her in the three concluding routines on the uneven bars, beam, and floor.
A statement from USA Gymnastics said Biles was suffering from an unspecified "medical issue" and faced daily assessment to determine whether she can continue her Olympic campaign.
"Simone has withdrawn from the team final competition due to a medical issue. She will be assessed daily to determine medical clearance for future competitions," the statement sent to AFP said.
The four-time gold medallist at the 2016 Rio Games qualified for all six finals available to her but her performance in qualifying on Sunday was littered with uncharacteristic mistakes.
In an Instagram post on Monday the 24-year-old said she sometimes feels like she has "the weight of the world" on her shoulders.