Viduka, who missed the start of this season because he was away with Australian playing in thev Asian Cup (and came back injured), had been due to have an injection for his long-standing Achilles injury on Thursday.
Is Viduka Worth The Effort?
Kevin Keegan: "If it's three months then he won't miss much of next season.
"We'll know more about that in 10 days time when he visits the specialist."
After making a U-turn after saying he was retiring from international football a year ago, he played for the Socceroos in the summer and has told his coach he will play in the World Cup qualifiers.
But then ruled himself out of the next three qualifiers ... and that was before he was injured.