First, Naomi Osaka declined to do press interviews for the French Open. For that she was sanctioned. Which caused her to withdraw from the tournament. That was in June.
Then at the Olympics this month (July 2021), Simone Biles withdrew from an Olympic gymnastic event.
In both cases, the reason was for their mental health.
Osaka did not like the format of the press conference which could be intimidating or confrontational - at least, from her perspective.
Biles simply said that she was not confident of herself. That she did not trust herself.
This is the woman who is so good, four moves in gymnastics are named after her.
[This is Katelyn Ohashi (video). She outscored Simone Biles a few years ago. But she left the sports after injury and some incident of body-shaming. ]
So when she says she's not confident, that she doesn't trust herself, it probably means something.