(Reuters) - World number three Carlos Alcaraz is unlikely to be at his best for Wednesday's ATP Finals match against Andrey Rublev as the four-times Grand Slam champion continues to struggle with illness, the Spaniard's coach Juan Carlos Ferrero said.

Carlos Alcaraz's performance in the ATP Finals is under threat as he battles illness, affecting his preparation for a crucial match against Andrey Rublev. Coach Juan Carlos Ferrero reveals the Spaniard's struggles with breathing,

Alcaraz is battling an illness and he was spotted training with a nose strip ahead of his straight-sets defeat to Casper Ruud on Monday. The four-time Grand Slam winner was completely out of sorts as he lost 6-1 7-5 in Turin.