Paddy McCartin has been subbed out of Sydney's AFL match against Port Adelaide in the opening minutes of the first term due to a concussion.
McCartin's head made contact with the ground after he was on his knees then launched forward while competing for the ball on a wing at the SCG on Saturday night.
The Swans key defender immediately grabbed at his head and was soon assisted by trainers, but then staggered and fell backwards when trying to get to his feet.
McCartin had to be helped from the field and was subbed out shortly after with Robbie Fox entering the contest against the Power.
The 26-year-old has a history of concussions but has re-emerged as a key defender since joining his younger brother Tom at the Swans.
McCartin was drafted to St Kilda with the no.1 pick in 2014 as a key forward but only played 35 games in five seasons marred by eight concussions.
He returned to playing with the Swans VFL team in 2021 and joined their AFL set up last year to be a critical part of their charge to a grand final against Geelong.
McCartin was also concussed after receiving an errant knee to the head against Hawthorn last year but returned for the Swans after completing the standard 12-day protocols.
