GWS have confirmed that co-captain Callan Ward is the latest AFL player this season to suffer an anterior cruciate ligament rupture.
Ward joins Richmond's Alex Rance, Adelaide's Tom Doedee, Collingwood veteran Lynden Dunn and several others whose seasons are over because of ACL tears.
Ward returned from a separate knee injury in Saturday's match against Geelong but he ruptured his left ACL in a tackle from Gary Ablett during the first term at GMHBA Stadium.
Ward was helped from the field and later was in tears on the bench.
It is a massive blow for the Giants, who scored their first win in Geelong.
Ward was all smiles as he celebrated with teammates post-match, but he now faces a knee reconstruction.
"This is obviously devastating news for Callan who is a tremendous leader of our club," said Giants football boss Wayne Campbell.
"His character and leadership of the club is highly valued and I have no doubt he'll continue to play a very important role in the coming months."