The star striker could face a race against the clock to be fit and in form for the tournament in Brazil after picking up a muscle problem on club duty
Cahill, 34, went off in the 27th minute of the Major League Soccer game at Red Bull Arena on Sunday.
"I'd probably get in trouble if I made any statements right now without consulting a doctor, but it looks like at least, the best-case scenario, a strain in the hamstring, worst case scenario a pull in the hamstring," Petke was quoted as saying by BigAppleSoccer.
"But I am going to the doctor now to figure that out."
Australia's World Cup campaign begins against Chile on June 13, giving the veteran forward just over two months to recover.