A SPECIALIST meeting on Monday is expected to rule Sydney defender Jack Maibaum out for the season after injuring his ACL last week.

Maibaum, 20, suffered the injury in training ahead of his third season on the Swans' list.

"Jack had been training really well over summer and was well primed for the season ahead, so clearly this is bitterly disappointing for Jack and for the team," Sydney head of football Charlie Gardiner said.

"He'll consult a specialist today to determine the prognosis and we'll map out a plan for his recovery from there."

Maibaum is yet to make his senior debut after two solid seasons in the Swans' NEAFL side.

His setback will provide the Swans the option to add another player to its list before the pre-season supplemental selection period shuts on March 15.

However, already holding one spot with the ability to place Kurt Tippett on the inactive list, the Swans may opt to hold the selections until the mid-season draft.

An underage All Australian defender, Maibaum was selected with pick 45 in the 2016 NAB AFL Draft and is set to fall out of contract at season's end.