The Sydney Swans will be without ruckman Callum Sinclair for Sunday’s clash with Fremantle in Perth.

Sinclair suffered a knee injury in a marking contest with Carlton ruckman Matthew Kreuzer in Sydney’s Round 18 win at the SCG.  

General Manager of Football Tom Harley says while Sinclair played out the match, scans later revealed a fragment of cartilage had broken.

“Callum suffered a little discomfort during and after the game, so he had a scan immediately after that,” Harley said.

“The scan revealed some cartilage had broken off in his right knee, so he underwent arthroscopic surgery on Tuesday morning to remove some of that floating cartilage.

“We won’t know the full prognosis until he recovers from the surgery, but we are hopeful he will be able to return within a month.”