Justin McInerney will miss at least eight weeks with a hamstring injury, leaving premiership hopefuls Sydney without both of their star wingers.
McInerney could miss up to 10 weeks after being forced out of the club's two-point win over St Kilda late in the opening half with hamstring tightness.
The in-form midfielder had risen to new heights in injured Errol Gulden's absence, meaning the setback looms as a massive blow for the second-placed Swans (11-2).
Sydney are at least hopeful Gulden - who hasn't played since round one - is on track to make his return from a shoulder injury in round 16.
Key defender Tom McCartin will also be sidelined after suffering another concussion against the Saints, joining Lewis Melican (hamstring), Dane Rampe (calf), Tom Papley (calf), Braeden Campbell (shin) on the sidelines.
