Scans on Monday will reveal whether experienced Sydney onballer Jude Bolton will miss the rest of the season with a knee injury.
Bolton limped from the ground with the help of a trainer during the third quarter and was immediately subbed out of his side's 22-point win over Carlton on Sunday.
One of only five 2005 premiership players left at the club, Bolton is a key cog in the Swans' push for September glory.
The 32-year-old, who has booted 20 goals this season, was kicking a ball out of the Swans' defensive 50 during the third term when Aaron Joseph came into to try and smother.
The Carlton defender made minimal contact with Bolton but when the Swan planted his left foot it landed awkwardly and his knee hyper-extended.
He spent the rest of the match on the bench icing his knee.
Asked whether Bolton had damaged his ACL, Sydney coach John Longmire said: "I don't know yet. He just needs to have a scan before we can see what the result is. It's a bit hard at the moment to say what it is."
The win boosted the Swans a game clear at the top of the ladder with four rounds left.
Their next test is a blockbuster against second-placed Collingwood at ANZ Stadium on Saturday night.
"They've been a tough side to beat for us for a fair while now and we think we've improved a bit," Longmire said.
"We're really looking forward to that, getting in front of our home crowd and taking on one of the better teams in the competition.
"It's an important game to be able to play a team that's played in Grand Finals previously ... and a team that's in really good form and it's a good challenge for our group.
"We've come up short in the past and Collingwood have been just too good for us and that's our challenge ... to try and lift and see if we can improve enough to catch those really good teams, which Collingwood are one of."