Chelsea defender Gary Cahill was treated in hospital this week for gastroenteritis and could miss Saturday's FA Cup semi-final with Tottenham, boss Antonio Conte says.
Reports on Friday said the England international spent two nights in hospital with a "mystery" illness.
"He arrived on the training ground with a bit of fever and our doctor preferred to take him hospital to check his condition," added Conte.
"Now he's getting better."
Gastroenteritis is a common condition that causes diarrhoea and vomiting.
Cahill has played in all 32 games to help Chelsea establish a four-point lead at the top of the Premier League with six games remaining.
"If you ask me for tomorrow my answer is it will be very difficult," said Conte on Cahill's chances of playing at Wembley.
John Terry, 36, could feature at some stage in the tie just days after announcing he was leaving the club in the summer, after more than two decades at Stamford Bridge.
"The problem is John wants to play regularly and for this reason I think we have to respect his decision," added Conte.
"If you are asking me if this is a serious loss then yes. I think so."
Conte described semi-final opponents Tottenham as a "great power" in England.
"For for the second consecutive year they are fighting for the title. Last season they missed it and they are trying again. They are full of great players," he said.