Carlos Alcaraz's coach, Juan Carlos Ferrero, has cast doubt over whether the Spaniard will be in a fit state to play his ATP Finals clash against Andrey Rublev tomorrow (Wednesday).

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.

One day on, the outlook is even bleaker for Alcaraz. According to Punto de Break, he completed just 10 minutes of light training today (Tuesday) before cutting it short and heading back to the hotel.

Ferrero then explained: "As soon as he moves a bit, he finds it hard to breathe. He has tightness in his chest. It's a bad time to fall ill. We can't predict whether he will play tomorrow or not."

The coach added that Alcaraz will do everything he can to complete his second match at this year's ATP Finals, while lowering expectations amid a tricky set of circumstances. "We've all played under these conditions," he said. "I don't think it will get to the point of not playing, but it will be difficult for him to be at 100 per cent tomorrow."

Alcaraz and his team will make a final decision on Wednesday morning. Tournament organisers have scheduled his match with Rublev for 2pm local time, making it a tighter turnaround than for Ruud and Alexander Zverev, who play in the evening.

Having lost to Ruud, Alcaraz could use a result against Rublev, who himself will come out fighting after being defeated by Zverev in his opening match.

Speaking after the Ruud loss, Alcaraz hinted that his illness is worsening. And his comments have been backed up today's early exit from practice.

"A few days before coming here, I got sick at home," he explained. "And yeah, the days that I was practicing here, I was feeling okay. Not great, but okay. I could play. I could feel that I can get into the rallies in the practice. Obviously, in the matches is totally different. But today, I didn’t feel well.

"In this morning, I feel uncomfortable in the stomach. After long rallies today, I couldn’t feel well. I don’t want to, you know, say because I don’t want to sound like an excuse. But if I feel bad, I feel bad."