McCartin was delisted by the Saints at the end of 2019 after numerous concussion issues saw him in need of a lengthy lay-off.
Swans GM of Football Charlie Gardiner told SEN’s Dwayne’s World that McCartin is a player of interest for the Swans ahead of next month’s Rookie Draft.
Longmire was asked on SEN Breakfast whether McCartin could join his brother, Tom, at the Swans in 2021.
“We’ve looked at him,” the Swans premiership coach said.
“We’re going into the draft and rookie draft in a couple of weeks with all options open. There’s been no guarantees made, we just need to make sure we keep everything open.
“We loved what Tommy’s been able to do us and the McCartin family are fantastic.
“We’ll see what happens on draft night and we’ve got to make sure we keep all of our options open.”
McCartin has also been linked with Carlton after undertaking a medical with the Blues.