Bolton Wanderers central defender Gary Cahill is set to miss the rest of the season due a blot clot in his arm.
The 24-year-old, who is on the fringes of the England senior squad, missed the weekend goalless draw with Fulham and has now been ruled out for several months.
Manager Owen Coyle confirmed: "Gary suffered a pain in his arm and it became severely swollen on the day of the game.
"There was no way he could play, so we took him straight off to hospital. It turns out he had a blood clot in his arm, so he is going to be out for a number of months."
"It is a severe blow for the boy but our main concern is his welfare. We have to make sure Gary is fit and well.
"He will miss the next few months, it might be for the rest of the season, we will hear from the specialist later.
"The clot needed to be resolved and in doing that you need the medication. It follows you can't play.
"I believe he would have made the World Cup for the summer, but we have to make sure first of all he recovers from this blood clot."
Newly-installed Trotters boss Coyle had recently stated that Cahill remaining at the club was one of the main conditions he sought to take up the job.
He said: "We have always been focused regarding Gary Cahill. I knew he wasn't going anywhere - that was one of the stipulations when I came here."
Cahill joined Bolton in for £5million January 2008 from Aston Villa and has since scored ten goals in 78 appearances in all competitions.