Greg Rusedski could face months out through injury, according to British Davis Cup coach Jeremy Bates.
Doubts have been raised about Rusedski's fitness for some time.
Now Bates believes the British number two will miss the Australian Open and Great Britain's Davis Cup tie in Australia that follows.
"Some players will play if they are 90% fit and I know Greg will only play if he is 100% fit and confident," said Bates.
"He wants to be totally confident before he plays again and I have heard a rumour that he'll be out for months."
Rusedski has not played since the US Open in September, and recently split from coach Sven Groeneveld for a second time as he was unable to name a comeback date.
He was originally scheduled to make his return in Doha on 30 December, but that now looks increasingly unlikely.
Britain's hopes for for the Davis Cup tie against Australia were dealt another blow with the news that number three Martin Lee has undergone a knee operation and is unlikely to be fit by Febuary.
Tim Henman is also coming back from a shoulder injury and his participation is in doubt, so captain Roger Taylor could be without his top three players for the clash.
Great Britain's main weakness has always been an over-reliance on Henman and Rusedski.
Australia, meanwhile, have been boosted by the news that Mark Philippoussis could be fit to play alongside world number one Lleyton Hewitt.