Sydney's undermanned defence is set to continue its uphill battle this week, with lockdown defender Robbie Fox ruled out of Saturday's matchup with cross-town rivals GWS due to concussion.

A third-quarter collision with Geelong's Mitch Duncan left Fox dazed on the Kardinia Park turf before the Swans flanker was able to play out the remainder of the contest.

A failed head injury assessment has since placed Fox out of action for the coming week, meaning John Longmire's already depleted defence will be another man down.

The Swans are no certainty to regain co-captain Dane Rampe (neck) or Tom McCartin (concussion) for Saturday's 'Battle of the Bridge', with Sydney's rearguard preparing for the difficult task of taming GWS' attacking third with another man down.

Lance Franklin is also needing to prove his fitness ahead of the Round 7 contest, having battled a knee issue in recent weeks. If Franklin were to be cleared to play, the veteran forward could move into Longmire's front six and allow recruit Aaron Francis to play in defence.

"We have to deal with what we can control and whether that's (with) a young squad like we had on the weekend, which was against a really experienced hardened team, or player availability," Longmire said.

"You've just got to get on with it and do some things that the game just requires, and that's what we're going to focus; on what we can control.

"We're not sure with Franklin, Rampe and Tommy McCartin just yet. Whether there'll be any availability this week from those three or not, we'll just have to wait and see.

SYDNEY, AUSTRALIA - JULY 04: Dane Rampe catches the ball during a Sydney Swans AFL training session at Lakeside Oval on July 04, 2019 in Sydney, Australia. (Photo by Jason McCawley/Getty Images)

"... We haven't had our first training session so we'll see how the week progresses. We're hoping that they'll start to get a bit of training tomorrow.

"Ultimately, they'll be assessed by the doctors whether they're available to play. With 'Foxy' not being available this week it'll just be influenced on whether they're ready to go."

The Swans have confirmed young midfielder Matthew Roberts will spend the coming weeks on the sidelines due to a medial ligament knee injury, with scans on Monday set to give the club a clearer understanding of the full extent of the setback.

Coupled with Fox's absence, the second-year Swan will be one of at least two outs for John Longmire's side heading into Round 7.

Veteran ruckman Tom Hickey returned to play over the weekend through Sydney's VFL side, who fell to the Northern Bullants on Sunday.

Under managed minutes, Hickey recorded 17 hit-outs and 13 disposals, however, Longmire stated the club remains "mindful" of his fitness following a period hampered by calf and hamstring injuries.

"He's 32 and coming back from three soft tissue injuries in a row," the premiership coach explained.

"We've just got to make these decisions based on what the team needs and what we'd like in a structural sense, but also what the players can actually do and whether they're right to play.

MELBOURNE, AUSTRALIA - MARCH 31: Tom Hickey of the Swans is tackled by Bailey Smith of the Bulldogs during the 2022 AFL Round 03 match between the Western Bulldogs and the Sydney Swans at Marvel Stadium on March 31, 2022 In Melbourne, Australia. (Photo by Dylan Burns/AFL Photos via Getty Images)

"Whether that's Tom, or Tom McCartin or 'Ramps' or 'Bud' or those guys, we'll have to make that decision on whether they can actually come in and contribute regardless of what the team needs."

Sydney and GWS will go head-to-head at the SCG on Saturday at 2:10pm (AEST).