Austin suffered the injury to his right knee on Friday training at Gosch’s Paddock, with scans later revealing the full extent of the damage.
"Austin and the club's medical staff will consult surgeons early next week," a club media release read.
"With Austin now on the long-term injury list the club will consider the possibility of signing an injury replacement for the remainder of the campaign."
The former Central Coast Mariners flyer had endured a mixed start to the season on the pitch, scoring a late equaliser away to Adelaide United in a 2-2 draw in round 3 but then seeing red in a 1-1 draw with Western Sydney Wanderers in round 5.