NAB AFL Rising Star winner Callum Mills has been ruled out of Friday night's preliminary final against Geelong with a hamstring strain.
Mills hurt his right hamstring in the Swans' qualifying final loss to Greater Western Sydney, and was never really a chance to prove his fitness in time to take on the Cats.
The 19-year-old ran laps at training this week, but never extended himself, and will now have to rely on his team winning through to next week's Grand Final to play again this season.
The season decider will be played just 21 days after Mills hurt himself in the first half against the Giants.
While the youngster won't make the trip to Melbourne, co-captain Jarrad McVeigh remains a chance to play, if he can show he's over the minor calf strain he suffered last week against Adelaide.
The Swans will have a light run in Melbourne on Thursday and are yet to rule out McVeigh, although the veteran is at long odds given the team's six-day break before the preliminary final.
Gary Rohan (knee), Kurt Tippett (jaw) and Zak Jones (concussion) are other injury concerns for the Swans, but should be right to take on the Cats at the MCG if selected.