Sydney will have to face St Kilda without star Sam Reid, with the key forward failing to get up for Saturday's home AFL hit-out.
Callum Sinclair has been recalled to take his place, leaving battling big man Kurt Tippett to play another week in the reserves.
Reid was given until Thursday's final training session to prove his fitness but couldn't overcome a groin strain in time for the Pride game at the SCG.
It's a blow to the Swans' hopes of a 10th win from 11 games.
"Sam tightened up early in the first quarter last week and actually pulled up okay during the week," coach John Longmire said.
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"Unfortunately, he couldn't do a lot at training today so that means he is out."
Longmire had considered rushing Tippett back into the firsts but has opted to send the out-of-favour 30-year-old to the NEAFL, where he'll attempt to play more than the half game he managed in last weekend's long-awaited return.
Instead, Sinclair has been handed a first start in four weeks and will do everything to re-cement a spot.
"He has been really good for our reserves and kicked nine goals over the last couple of weeks," Longmire said.
"His form in the ruck was solid for us before he went out of the team and we know he's a good marking target for us in the front half so he gets another opportunity.
"He was actually in good form before he went out of the team."
Forward Gary Rohan has also made the cut after enduring a hamstring issue in the Swans' 13-point derby triumph over Greater Western Sydney, although utility Harry Cunningham (foot) remains at least another week away.
The sixth-placed Swans will host St Kilda in the knowledge they haven't lost to the Saints in more than five years.
Yet while the hosts are red-hot favourites for the Pride match, they sit on equal points with Alan Richardson's ninth-placed side and can ill afford a slip-up.
"To the players' credit, they've played a pretty strong brand of footy now for a couple of months and been really consistent," Longmire said.
"It's got us back to a position we prefer to be, knowing we still have a fair bit of work ahead of us."
