England midfielder Gareth Barry has been ruled out for up to four weeks with ankle ligament damage.
The Manchester City man picked up the injury in his side’s 1-0 defeat to Tottenham on Wednesday.
The layoff makes Barry a doubt for the World Cup finals which are due to kick-off in five weeks time.
The initial diagnosis of the knock was that the 29-year-old had only suffered a sprained ankle but tests on Friday revealed the injury was worse than first feared.
Capello has regularly insisted that he will only consider fully-fit players in his 23-man squad for the competition, which he will name on 1st June.
City manager Roberto Mancini said: “I feel very sorry for him.
“Gareth is a fantastic guy and a fantastic player.
“I hope he can play in the World Cup but Fabio Capello and his medical staff must decide.”