THERE'LL be no reprieve from the key defensive crisis engulfing Sydney as the Swans try to restrict arguably the best tall forward duo in the AFL on Friday night.

Full-back Tom McCartin has been ruled out again for the Swans due to concussion symptoms, joining brother Paddy on the sidelines as the older sibling's playing future remains up in the air.

With Dane Rampe also out due to a neck injury, Sydney are yet again without their three premier key defenders for the clash with Carlton's Charlie Curnow and Harry McKay at the SCG.

"There's three of our starting six from last year. We've just got to keep making do. We think (Aaron) Francis has come in and done a reasonable job, we'll take a look at (Lewis) Melican who's played the last couple games in the VFL," coach John Longmire said.

"We've just got to make do against what we know is a couple of the best marking forwards in the competition who are both Coleman medallists."

The continued absence of Tom McCartin, who finished sixth in the Swans best and fairest last season in a Grand Final year, is becoming a growing concern.

While the concussion issues of his older brother are well known, Tom will now have played just two of Sydney's past seven games having suffered a head knock against Port Adelaide in round four.

"Yeh, it's going for a bit longer than what we hoped. It is what it is, we've just got to let the symptoms resolve completely. He's doing a bit of exercise and hopefully he can ramp that up through the bye period and then we'll see what happens post bye," Longmire added.

Tom and Paddy McCartin at Sydney training on May 11, 2023. Picture: Phil Hillyard

There are a litany of injuries at the Swans to key position players; the ankle injury suffered by ruckman Peter Ladhams in the win over North Melbourne will sideline him for several weeks and will see him join both McCartins, Rampe, Logan McDonald, Joel Amartey and Sam Reid on the sidelines.

Reigning best and fairest winner Callum Mills is also out, but Tom Hickey (concussion) may return if he gets through training this week.

If so, he'll partner young ruck Lachlan McAndrew, who is confirmed to play his second AFL game against the Blues.

The Swans have been boosted by their chaotic and controversial last-minute win over North Melbourne last week to help provide them with some momentum ahead of an encounter with the Blues that will have a huge bearing on the top eight chances of both clubs.

The performance of Lance Franklin was critical in the victory as he finished with three goals and nine marks to hit back after some criticism following the loss to Fremantle the previous week.

"He was really crook the week before so sometimes there's reasons behind it," Longmire said.

Lance Franklin and Dane Rampe celebrate Sydney's win over North Melbourne in R10, 2023. Picture: AFL Photos

"He was fantastic, he was probably the best forward on the ground. His last quarter he just lifted, played the whole quarter, went up the ground, charged around. He just wanted to win, he bounced back like we thought he would."

Longmire was also dismissive of criticism levelled at Isaac Heeney this season, who has just ten goals from ten games following 49 last year in what was an All-Australian campaign.

"We've also had some personnel challenges. His last year is off the back of a different team. He also does some things that don't get acknowledged but as far as commenting on analysts, that's not my go with all due respect to analysts," he said.