French Open and Wimbledon champion Carlos Alcaraz's continued participation in the ATP Finals in Turin is in doubt after he withdrew from training due to illness.
His coach Juan Carlos Ferrera told Spanish media that the 21-year-old stopped playing after just five minutes after complaining of chest pain that made it difficult for him to breathe.
Alcaraz is scheduled to play Andrei Rublev on Wednesday.
Russia's Daniil Medvedev won his first indoor match since last year's final with a 6-2, 6-4 win over Alex de Minor (Australia) to keep his chances of reaching the semi-finals of the event alive.
/DB/