Bolton defender Gary Cahill could miss the rest of the season after suffering a blood clot in his arm.
It is a devastating blow for Cahill, who was hoping to claim a place in England's World Cup squad.
The 24-year-old was taken ill on Friday and sat out the 0-0 draw against Fulham on Saturday.
Manager Owen Coyle said: "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."