Australian midfielder Mile Jedinak, who is expected to be named the national captain this week, has sent an injury scare through the World Cup squad after limping off in Crystal Palace's 2-2 draw with Fulham.
Jedinak appeared in pain when he was substituted after 59 minutes with a groin strain and he is set to undergo scans this week to determine the extent of the problem, Football Federation Australia said on its website.
Reports said he would not be able to train or play before the squad reaches Brazil, which would rule him out of the Socceroos warm-up against South Africa in Sydney on May 26.
National coach Ange Postecoglou will name Australia's 30-man preliminary World Cup squad on Wednesday with Jedinak widely tipped to become captain after veteran Lucas Neill was informed last week he was no longer needed.
Jedinak, 29, wore the skipper's armband in the Socceroos' most recent match against Ecuador in March.
The injury brought to an end his impressive record of playing in every single minute of the Premier League season for Crystal Palace.