Captain Nathan van Berlo will be sidelined for up to a month after scans revealed bone bruising around his knee joint.
Van Berlo, 26, was substituted during the third quarter of Balfours Showdown XXXIV on Sunday.
He was initially expected to be available for Sunday’s clash with the Western Bulldogs, but scans showed the damage was worse than first thought.
The hard-running midfielder will miss his first game since Round Four, 2010, bringing to an end a streak of 68 consecutive matches.
General Manager of Football Administration Phil Harper said the skipper would be missed.
“It’s disappointing for Nathan to sustain such an injury,” he said.
“However, it will be a great opportunity for all our players to step up in the captain’s absence and display leadership qualities to help fill the void.
"We think we've had plenty of guys in form in the SANFL; straight to mind comes (Tom) Lynch, Jarryd Lyons from Glenelg, Sam Kerridge from Sturt, Rory Laird from West Adelaide - so there's plenty of guys who would be putting their hand up to take a spot that's available," Harper said.
"There's a lot of guys in form in the SANFL and some of them need to be rewarded. All those guys would be capable but there are already guys who are in the team who could go into that role."