Carlos Alcaraz's coach Juan Carlos Ferrero issued a concerning update about his players' health following the world No 3's recent struggles.
Alcaraz slumped to a shock 6-1, 7-5 defeat to Casper Ruud in his opening match at the ATP Finals on Monday and after the match he revealed that he had been battling with a cold in the build-up to the match.
"In this morning, I feel uncomfortable in the stomach. After long rallies today, I couldn't feel well," he explained. "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. It is what happened today."
Despite his woes, the four-time Grand Slam winner returned to the training court a day later, but his session against Andres Martin lasted only 10 minutes before he called it quits as he was still feeling poorly.
It set off alarm bells that he could withdraw from the remainder of the tournament.
The 21-year-old is due to face Andrey Rublev in his second round-robin match on Wednesday afternoon before taking on Alexander Zverev in his final group encounter on Thursday.
Ferrero has confirmed that Alcaraz is still struggling to breathe and has chest problems, but he has given a positive update about his player's chances of facing Rublev.
"As soon as he moves a little, it's hard for him to breathe. His chest is a bit tight. It's a bad time to get sick," he said.
"We should not anticipate whether or not he will play [on Wednesday]. We have all played in these circumstances. I don't think he's going to be so bad that he won't be able to play. It's going to be difficult for him to be 100% [on Wednesday]."
Ruud admitted that he took advantage of Alcaraz's struggles during their match as he "tried to make him play rallies", adding: "I knew he was maybe dealing with a bit of a cold. I've seen him snuffling around in the area here and always with a tissue for his nose.
"Of course, that's sad, that's not good for him, but it's also part of the game and I knew it coming in."
Ferrero says extended points are a big concern for the Spaniard at the moment.
He added: "Rublev is a player who moves a lot, you have to be very good on your legs and, right now, that's what's costing him a little more, recovering between points … "
