There are concerns about the future of Tom McCartin, who suffered a concussion in Sydney's clash with St Kilda.
McCartin has missed 15 games with concussion since the start of 2023.
He collided with Liam Ryan backing into a contest midway through the third quarter, with play stopping to enable him to come from the field.
At minimum, he will miss Sydney's next game against Port Adelaide, before the Swans have the bye.
Tom's brother, Paddy, was forced into early retirement in 2023 due to concussion, with his own history causing concern about the head knock.
McCartin has been in All Australian form this season, averaging 21 disposals and six spoils for the top-two Swans.
Jai Serong was the hero as Sydney won by two points, reclaiming the lead for the first time since the first quarter when Serong snapped through a goal with just 14 seconds on the clock.
The Saints seriously tested Sydney, with their three much talked about recruits all having a say in what was on track to be a significant upset at the SCG.
