IN-FORM Sydney midfielder Justin McInerney will be in a knee brace for several weeks but his return date remains unclear in a huge blow for the Swans as they look towards finals.

McInerney suffered a posterior cruciate ligament (PCL) injury to his left knee in their 79-point win against North Melbourne on Saturday.

Scans to assess the damage have been delayed due to swelling, but coach John Longmire has confirmed he will be out for the short term.

The 23-year-old has enjoyed a career-best season for the Swans, showing his versatility and impressing on the wing, off half-back and during some stints on the ball.

"He will be in a brace for a couple of weeks and then we'll see how he goes from there," Longmire said.

"PCLs can be a bit unpredictable so we're not sure what that means.

"It's at least a couple (of weeks) and how much beyond that we're not sure.

"Hopefully it's not a long time because he's such a valuable player for us. He's been outstanding for us this season."

Sydney will at least welcome back superstar Isaac Heeney from a one-game suspension for Sunday's clash against Brisbane as Longmire juggles selection headaches around the returns of Luke Parker and Callum Mills.

Meanwhile, Longmire says assistant coach Dean Cox remains focused on Sydney as momentum grows for the West Coast legend to return home.

The Eagles have already begun the search for former coach Adam Simpson's full-time replacement, with Cox emerging as the early frontrunner to replace interim boss Jarrad Schofield.

Former ruckman Cox played 290 games, including the club's 2006 premiership triumph, for West Coast from 2001 to 2014 before joining Simpson's coaching panel. The 42-year-old then made the move to Sydney in 2017.

Cox has since become an integral cog in the Swans machine and has been widely tipped to be the likely successor to Longmire when the 2012 premiership coach ends his long tenure at the club.

"First and foremost, we don't get really dictated to by what other clubs do or what is going on in other clubs," Longmire said when asked of the club's coach succession plans.

"Second of all, it's great that Dean's invested in us.

"When you've got a quality assistant coach like 'Coxy', it's great to have him so invested in this footy club.

"I'm sure if those conversations (between the Eagles and Cox) happen at some stage, he'd come and talk to us, but he's completely focused on us.

"We're more than comfortable where it sits."