The Western Bulldogs are unsure when forward-turned-defender Josh Bruce will return to play after suffering "significant damage" to his ribs in Round 5.

A knee to the ribs during Saturday's loss to Port Adelaide has sidelined the 30-year-old for the coming weeks, with Bruce required to visit a specialist to aid his rehabilitation after injuring multiple ribs in the collision.

The Dogs confirmed on Tuesday morning that Bruce's return timeframe is unclear, with a better grasp on his likely recovery to come in a matter of weeks.

“In the third quarter of the game on the weekend, Josh went to ground in a contest and received direct contact from an opposition knee straight into his ribcage,” Bulldogs sports medicine boss Chris Bell told westernbulldogs.com.au.

“Unfortunately this has caused significant damage to multiple ribs in Josh's chest.

“Josh has returned to Melbourne – we're seeking specialist advice on how to best manage him.

“We aren't going to set a time-frame at the moment, but hope to update more specifically in the next couple of weeks."

Bruce will join a list of key Dogs currently sidelined through injury, with gun midfielder  Bailey Smith set to miss this week's contest with Fremantle due to a calf issue.

Smith did not play against Port Adelaide due to the injury and is expected to make his return either next week or Round 8 at the latest as he battles with calf tightness.

Key defender Alex Keath is no certainty to replace Bruce in Luke Beveridge's backline as he looks to return from a concussion sustained in Round 4 against Richmond.

The former Crow will need to prove his fitness in the coming days before the Dogs fly out to Perth for Friday's clash against the Dockers.

He joins utility Laitham Vandermeer, who suffered a broken fibula in the pre-season, as tests for this week, while Hayden Crozier has been cleared to play after nursing a back issue.

The Bulldogs will face Fremantle at Optus Stadium at 8:10pm (AEST) on Friday night.