Tom McCartin has suffered another concussion, adding to his family's terrible AFL history with head knocks.
Sydney also lost Justin McInerney to a hamstring injury and several teammates were sore after Sunday's pulsating two-point win over St Kilda at the SCG.
McCartin bravely went back with the flight of the ball in the third term and Saints small forward Liam Ryan cannoned into his back.
Swans coach Dean Cox revealed there was no assessment for McCartin before he was ruled out of the game.
"If you are out for a period, you fall straight into the concussion protocols," Cox said.
McCartin has missed several games through concussion, most recently last year. His brother Paddy was forced to retire prematurely three years ago because of his concussion history.
