Fremantle coach Justin Longmuir says he doesn’t have any concerns around ruckman Sean Darcy’s long-term durability despite conceding his latest calf injury was worrying.

In a dire sign for the ruckman’s fitness, Longmuir revealed Darcy sustained the fresh setback in a rehabilitation session on Saturday while he was in concussion protocols, which forced him to miss the western derby victory against West Coast.

It is the same injury that the 27-year-old sustained in the pre-season and forced him to miss much of the lead-up to the season before he was picked for round one.

“He did it in a rehab session on Saturday. It is really unfortunate. I’m disappointed for him,” Longmuir said.

“He’s clearly frustrated. It’s the same calf he hurt over the summer, so we’re expecting a similar timeline (on his recovery).

“It’s concerning, unfortunate, disappointing — whatever word you want to put to it. I’m not around the full specifics of when he did it or how fast he was running, but he’s done it in, rehab it, and move on.

“He’s frustrated, we’re frustrated for him. We need to get it right, and there’s still a lot of footy to be played this year.”

Darcy has missed at least seven games in each of his past three full season due of a series of injuries, and he is now facing an unknown amount of time on the sidelines as Fremantle pursues the top of the table.

The injury-prone ruckman still has another four years left on a six-year extension he signed in December of 2023, which will have him at the club until he is 31.

Longmuir shut down any thoughts that Darcy’s long-term future was at risk despite his inability to play regular football.

“I don’t really live in that space, like long-term. I think about the short-term for Sean right now,” he said.

“I know Sean can have a big impact for us at AFL level. He’s a best-and-fairest winner.

“Clearly, it’s been frustrating for us and him that he hasn’t been able to get continuity, but I can see that changing. So I do not have any concerns like that.”

Darcy’s absence has opened the chance for former Collingwood cult hero Mason Cox to embed himself in the premiership fancies’ best 23 moving forward.

Cox had an inauspicious Dockers debut in the 46-point win against West Coast on Sunday, but given Longmuir’s preference to play another ruckman alongside superstar Luke Jackson, he is likely to remain in the team to play Carlton on Saturday night.

“We’ve liked our policy because it gives Luke an opportunity to play in other positions,” he said.

“It gives us more flexibility to move the magnets around in-game as well. If we feel like we need something up forward from Luke or in the midfield from Luke.

“We probably expect Coxy to do a similar role to Sean or a similar role to what he did on the weekend. He gives us a bit more flexibility with his ability to play a few more minutes forward as well, so we’ll keep exploring what it looks like, but I was happy with his game at the weekend. He just didn’t maximise his opportunities.”