Serbia & Montenegro defender Nemanja Vidic will miss the Group C match against Argentina on Friday after suffering a knee injury in training.
The Manchester United player, who was due to return to the lineup after suspension, damaged his knee after sliding to collect a loose ball in training.
He was carried off in a lot of pain and while at first the injury was not thought to be too serious there are now concerns that he may miss the rest of the tournament.
Vidic was suspended for Serbia & Montenegro's opening 1-0 defeat by the Netherlands on Sunday.