Sydney have suffered a horror blow to their ruck stocks after Sam Naismith ruptured his ACL at training on Wednesday.
The news further decimates the Swans' depth after Kurt Tippett retired in late January, with AFL rules dictating Sydney cannot replace either player with a top-up from the state leagues.
Naismith, 25, played 15 games last year, averaging nearly 28 hit-outs per contest, and loomed as a significant part of the team for 2018.
“Obviously this is a disappointing setback for Sam so close to the start of the new season,” Swans football boss Tom Harley said.
“Sam was involved in a fairly routine training drill when his knee innocuously twisted, causing a rupture of his anterior cruciate ligament.
“While this is an unfortunate injury for Sam, we know he’s an absolute professional when it comes to his preparation and recovery and he will no doubt do everything possible to make sure he recovers from this injury.”
Sydney's ruck load will be shouldered by former West Coast Eagles player Callum Sinclair and youngster Darcy Cameron, who comes highly rated but is untested at AFL level.
Key defender Aliir Aliir and 190cm midfielder Dean Towers could come into calculations.
Sinclair averaged nearly 18 hit-outs and kicked 14 goals in his 19 games last year.
Naismith's strong 2017 season came on the back of forcing his way into the team from round 16 through to the grand final in 2016.