Melbourne - Stuart Appleby may be forced to pull out of his Australian Masters title defence because of a long-term back injury, he said on Tuesday.
A nine-times winner on the US PGA Tour, Australian Appleby is preparing to go up against a field that includes world number one Luke Donald at the Victoria Golf Club this week.
But Appleby, ranked 161st in the world, said chronic pain in his lower back had prevented him from practising his swing and put in doubt his participation in the A$1.5 million tournament.
"I haven't done many withdrawals prior to first rounds," the 40-year-old told reporters on Tuesday.
"I don't know my body well enough to know whether I can manufacture something from an ad hoc swing or whether it's a futile fight that I need to try another day.
"I'll make that decision closer to the time."
The tournament, won by Tiger Woods in 2009, will tee off on Thursday.