Fremantle have all but ruled out star midfielder Hayden Young as they prepare for a top-two blockbuster against Sydney.

Optimistic Young will prove his fitness quickly after his latest groin injury, Dockers coach Justin Longmuir could only lament a five-day turnaround between last week's defeat to GWS and this Thursday's clash against the Swans.

Young, who has played just nine games this season, hurt a groin in the ladder-leading Dockers' shock loss to GWS on Saturday and finished the match on the bench.

Longmuir is adamant the 25-year-old midfielder wouldn't be ruled out of action for long, holding out some hope for his appearance against the Swans.

"He'd be a chance to get up if it wasn't a five-day break," Longmuir said on Tuesday.

"A five-day break is going to make it pretty tight for him.

"We'll see how he feels today, but yes, I don't think this is going to be a massive setback."

Should Young prove his fitness, his inclusion will be a massive boost against Sydney's star midfield of Isaac Heeney, Chad Warner, fit-again Errol Gulden and ruck Brodie Grundy.

Heeney was outstanding with 27 disposals, eight clearances and a goal, while Grundy monstered the Western Bulldogs with 60 hitouts.

Longmuir wasn't willing to give up their game plan for the Swans' engine room.

"Yeah, we have to work that out later," Longmuir said.

"You can't lock down on everyone. You've got to trust your players that you've got out there, and you trust your system as well.

"It'll be a balance. We've also got - Curnow's had an outstanding year, Grundy in the ruck, (defender Nick) Blakey. They've got good players all over the ground.

"It's balanced between stopping individuals and trying to stop a system, so we'll strike that balance."

Longmuir will reunite with Swans counterpart Dean Cox after serving as his assistant for this year's State of Origin game, sharing the WA coaches' box.

"It's probably a bit hard to say, unless you're internal and you're across the day-to-day," Longmuir said.

"He likes throwing things around. Especially when I was working with him, he's a good relationship builder and really good at the technical side of the game.

"He doesn't mind moving the magnets, looking at the way that they've played this year.

"He's tried different things across the course of the season, probably expect the same this week."