US superstar Simone Biles pulled out of a second Tokyo Olympics gymnastics competition to protect her mental health on Wednesday, raising serious doubt over her participation in the rest of the Games. 

A day after her shock exit from the team event, USA Gymnastics said Biles, 24, had also withdrawn from the individual all-around competition at the Ariake Gymnastics Centre. The American arrived in Japan as one of the headline acts of the pandemic-postponed 2020 Games, shouldering an immense weight of expectation as she pursued a record-equalling nine career Olympic titles. But she withdrew from the team competition after a shaky opening vault, and her struggles mean she may be unable to add to the four gold medals she won at the 2016 Rio Games.