Alcaraz beat Safiullin in straight sets as Corretja said the main challenge may be mental, not physical.
US Open withdrawals have mounted, and the ATP Tour has responded to growing injury concerns.
Djokovic fell early at the US Open, and Brad Gilbert urged a schedule change after the defeat.
Alcaraz returned to singles with a straight-sets US Open win over Safiullin.
Djokovic moves on after a first-round US Open loss and is already entered for Beijing.
Toni Nadal is working with Alex Eala in New York before her opening US Open match.
Tsitsipas reacts sharply to Kyrgios’ positive test, saying he expected the news before the announcement.
Djokovic’s brief New York message followed a bruising US Open defeat and fresh questions.
Henman and Bartoli react to Djokovic’s US Open exit, with concern over his physical condition.
Roddick condemns Atmane after a heated exchange with the trainer at the US Open.
