Sydney is sweating on the fitness of Nick Blakey after sustaining an ankle injury against North Melbourne on Saturday night.
Blakey has been a revelation playing at half-back since returning to the team in round 16 after a spell in the VFL.
He was impressive again in the opening three quarters against the Kangaroos as he gathered 20 disposals, until his right ankle was stepped on in a marking contest just before the final break.
The 21-year-old tried to play on but had to be helped from the field and was soon subbed out. He was seen walking in a moon boot after the Swans' 14-point win.
"He was very good. He's only played about seven games in defence in his life, so he's still learning what that's about. I thought he was very important for a fair bit of the game until he got hurt," coach John Longmire said.
"It's disappointing he hurt his ankle, obviously it didn't look great and we'll have to see how the scans go.
"It was bad enough to sub him, we think it's not just a roll. We've got our fingers crossed that hopefully it's not too bad, but it swelled up pretty much straight away."
Longmire is hopeful that Josh Kennedy has avoided a hamstring strain despite the co-captain grabbing at the back of his leg and leaving the field with less than two minutes remaining in the match.
The Swans have had a fortunate run with injury for much of the season but could have several key players sidelined with only one match to play before their first finals series since 2018.
Lance Franklin was rested against the Roos while Jake Lloyd was ruled out due to ongoing knee soreness. Longmire said both are expected to play next week against Gold Coast.
But he was less confident that Callum Mills would return, after the gun midfielder missed for a second week due to Achilles soreness.
Sydney were forced to withstand a second half surge by North Melbourne, with the lead coming to within a goal in the final quarter, before two crucial majors to Will Hayward and a secured the victory.
"Particularly early, we jumped out with that real intensity and our pressure was at a really high level that first quarter," John Longmire said of the side's pressure.
"I thought that set a good scene for us when we were able to keep the ball in our front half.
"We dropped a little bit in that third quarter, and they were challenging us in the last, and we went again (particularly with our contested footy), and started to ramp it up again so that probably correlated to the scoreboard in our pressure and our ability to win the contest throughout the game.
"I think we just lifted our intensity and Tom Hickey played a good 10-minute period there and really lifted when they got within a kick. He and Will were really important so we were able to, when challenged, kick away again and that was a really good sign," Longmire added.
"The ability to steady and absorb it and kick again, lift the intensity and go another gear."
