Gary Cahill was treated in hospital for a small kidney stone and is a major doubt for Chelsea's FA Cup semi-final, boss Antonio Conte has said, but captain John Terry is unlikely to replace him.
England defender Cahill arrived at training on Tuesday with a fever and was admitted to hospital before being released two days later after undergoing tests.
Chelsea are to meet Premier League title rivals Tottenham at Wembley on Saturday and, while Conte stated that Cahill's illness is not serious, the Italian does not envisage him being fit to play.
"This period is not a lucky period for us," he told a pre-match news conference.
"When we started to have training on Tuesday he arrived at the training ground with a bit of a fever and then we preferred our doctor to bring him in the hospital and check his condition.
"It is not a serious problem, but now Gary is getting better and improving a lot. If you asked me for tomorrow [Saturday] my answer is very difficult, very difficult.
"Yes, [he had] a fever but then he had a problem, but not a serious problem but the doctor preferred him to be in the hospital and solve the problem."
With Cahill set to miss out, Chelsea have a void in their three-man defence but Terry, who announced last week that he is to leave the Blues after 19 years at the club, is not necessarily guaranteed to come in.
"This is a semi-final and in the season we tried to have in every position two options," Conte added.
"I think the right position for John when we play with three centre-backs is in the centre and the player playing there now is David Luiz.
"I have to make the best decision for the starting 11, we tried different solutions."
Conte can understand why so many fellow Premier League managers have expressed their interest in signing Terry, whose lengthy list of accolades include four league titles and a Champions League winner's medal.
"I'm not surprised about this. I am repeating in every press conference that John, in my first season, is very important, he's helping me on the pitch and off the pitch," he said.
"For us he's a good captain and the problem is that John wants to play regularly. For this reason, I think that we have to respect his decision because I was a footballer and I know when you arrive at this point of your career, and your mind and body told you continue, you feel you can continue and can play regularly.
"We have to respect his decision. If you ask me next season is it a serious loss, I think so."