Australia defender Patrick Kisnorbo is set to miss the World Cup after picking up an Achilles injury playing for Leeds on Monday night.
Kisnorbo buckled in pain after only six minutes of his side's home defeat against promotion rivals Millwall and was carried off on a stretcher.
Leeds manager Simon Grayson said: "I am absolutely gutted for the lad. Paddy's dream was to play in the World Cup and it looks like that dream has been shattered.
"Unfortunately he picked up a severe Achilles injury which will rule him out for the rest of the season and probably the World Cup as well. It is a huge blow for Paddy who has been a real warrior for us this season."
Kisnorbo had been expected to be named in Pim Verbeek's Socceroos squad for South Africa.