Aston Villa captain Stiliyan Petrov has been diagnosed with acute leukaemia, leaving English football in shock over a player's ill-health for the second time this month.
The 32-year-old Bulgaria international has not trained since playing against Arsenal last week.
The condition was diagnosed following tests after the midfielder developed a fever.
Petrov's illness is the second major health problem to have affected a Premier League player this month.
Bolton Wanderers midfielder Fabrice Muamba suffered a cardiac arrest on the pitch during an FA Cup game at Tottenham Hotspur two weeks ago but on Friday tweeted a picture of himself after a remarkable recovery.
Villa are due to host Chelsea in the Premier League on Saturday and coach Alex McLeish says the game will go ahead according to Petrov's wishes.
He says the players will be gutted but hopefully galvanised for the game for their captain.