Melbourne defender Colin Garland is feared to have torn his anterior cruciate ligament in a pre-season hit out.
Garland was playing for the Casey Demons in a warm-up clash against Port Melbourne at Casey Demons when he had to be stretchered off with an injury.
The injury is believed to be a torn anterior cruciate ligament, it has been reported.
The 28-year-old will have scans to confirm the extent of the injury.
The Demons already have injury concerns down back, with recruit Michael Hibberd and fellow defender Sam Frost both ruled out of their round one clash with St Kilda.
Casey defeated Port Melbourne by 44 points, 17.6 (108) to 10.4 (64), in the match, with Dom Tyson, Jack Watts, Jeff Garlett and Dean Kent all pressing their claims for round one.
Garland has played 141 games for Melbourne.