Gymnastics superstar Simone Biles was replaced in the US team after starting Tuesday's Olympic women's team final.
The four-time gold medallist at the 2016 Rio Games produced a lacklustre opening vault and then briefly left the competition floor, before returning to join her teammates.
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"Simone has withdrawn from the team final competition due to a medical issue.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,"
But she was replaced in the three concluding routines on the uneven bars, beam, and floor.