MELBOURNE, AUSTRALIA - SEPTEMBER 22: Zac Williams of the Giants kicks the ball during the Greater Western Sydney Giants AFL training session at Melbourne Cricket Ground on September 22, 2017 in Melbourne, Australia. (Photo by Michael Dodge/Getty Images)

GWS defender Zac Williams has reportedly ruptured his Achilles during a training session on Friday morning.

The injury could potentially rule Williams out for the entire 2018 season depending on the severity of the injury, which would be a massive blow to the Giants before the season has even begun.

With running defender Nathan Wilson heading to Fremantle during last season’s trade period, the Giants would have seen a bigger role for Williams this season, who plays a similar style to his former teammate.

Williams has played 76 games for GWS since making his debut in round five, 2013, and averages 18.64 disposals and 2.4 rebound 50s per game over his career.