GWS defender Adam Kennedy is expected to miss 12 months of football with a torn anterior cruciate ligament.
Kennedy hurt his left knee in a marking contest in the first quarter against St Kilda on Friday night.
He tried to stay on the field, but ultimately went off the ground and down to the rooms.
The club feared the worst after the game, which scans have confirmed this morning.
Damian Barrett shared the news on the Saturday Rub.
"Adam Kennedy of the Giants has been confirmed to have done his ACL," he said on Triple M.
"That would be a 12-month injury, you would seemingly think."
GWS head of athletic performance David Joyce said it was awful news for Kennedy.
“This is devastating news for Adam who’d started the season very strongly," he told gwsgiants.com.au.
"We’re confident that Adam will approach his rehabilitation with the same diligence and energy that he does every other aspect of his football.
"He’s a really popular member of the playing group and the whole club is right behind him."