Fremantle coach Justin Longmuir conceded they will be taking a cautious approach over Sean Darcy’s latest injury as the Dockers prepare to face an unknown Western Bulldogs outfit.

Darcy suffered a calf injury while working his way through concussion protocols, with the club listing him at 3-5 weeks away from returning to the field.

It’s the latest setback for the 27-year-old, who has played just 24 out of a possible 54 games since signing a mega contract extension after the 2023 season that has him locked in at the Dockers until 2030.

Longmuir said it would more likely be the latter figure as they look to get on top of the repeat injury.

“We’ve listed at about 3-5 weeks, so there’s a little bit of scope for a quicker recovery there,” Longmuir told 7NEWS.

“It’s a similar injury to what he did over the pre-season, so we’ll be a little bit more cautious since it’s a recurrence, so he’s got a little bit of time left on the sideline.

“But he’s positive and approaching it really well and really keen to come back a better player than he was at the start of the year.”

It gives Dockers recruit Mason Cox a clear window of opportunity to nail down his spot as the No.2 ruckman, having kicked two goals in the 14-point win over Carlton along with eight hit-outs.

While Cox is not expected to match Luke Jackson’s exploits, Longmuir highlighted why having a strong second option was important, allowing him to manage Jackson’s explosiveness.

“(Jackson) can do some things that not a lot of others can do on the footy field,” he said.

“I think his follow-up work shows what he can do, and he had a few of those moments throughout the game, and that’s why we don’t play him those long minutes in the ruck so he can have that energy and be a game changer for us.”

It comes as Fremantle are preparing to face an unknown Bulldogs outfit, with several key players listed as tests for Friday night’s clash at Marvel Stadium.

West Australian forward Aaron Naughton is a test after his sickening fall while attempting a mark, with scans clearing him of any nerve damage.

Star ruckman Tim English is also a chance to return from a knee injury, and could provide a big test for Cox, while speedster Arthur Jones is also a test following a hamstring strain.

Longmuir said regardless of what the final Bulldogs line-up will be, he will be preparing for their best.

“It makes them a little bit unpredictable, but we’ll scout them to have all those players,” he said.

“Like I say every week, we expect the Dogs to be at their best and even if some of those players don’t get up, they’ve still got a lot of weapons in that team and one of the best midfields in the comp.

“So we’ll be preparing for them at their best and readying for a four-quarter effort from us.”