Sydney will be without defender Dane Rampe for at least five weeks after he suffered a broken arm in a freak training accident on Monday.

The 2016 All Australian tripped and fell while doing some recovery running with teammates outside the SCG and has a small crack just below his elbow.

Coach John Longmire said losing one of his vice-captains in such unique circumstance was a massive disappointment ahead of Friday night's crucial clash with the Western Bulldogs.

"I sat down did the game review with him about 9.30 this morning, he then went for a run with the team an hour later, jumped over a chain on the way back and landed on his arm," he said.

"At the moment I've been told it looks like a five-week injury.

"I couldn't believe it to be honest, one of our guys from our media department saw it happen.

"He tried to jump the chain and mistimed his jump and fell on the concrete 25 metres from the front door (of the Swans' offices)."

Rampe's injury looks likely to open the door for exciting tall defender Aliir Aliir, who wasn't selected for the Swans' loss to Port Adelaide as he continues his way back from a toe injury.

Aliir played no part in the JLT Community Series but has built up his match fitness after playing the last three games in the reserves.

"His senior form last year came on the back of some strong reserves form, and he hasn't displayed that kind of consistent form over the last few weeks, but he obviously has to be in the mix," Long mire said.

Luckless midfielder Dan Robinson will be another Swan missing against the Dogs after he broke his left collarbone in the first half against the Power.

Robinson played the first seven games of 2016 before suffering the same injury against Essendon at the SCG, and wasn't seen at senior level again for the season.

"It's unfortunate because he did a really strong rehabilitation (last year), but got hit in exactly the wrong spot," Longmire said.

"He'd got back to playing some good football over the pre-season as well so he just has to get back on the horse and go again."

Longmire said that draftee Will Hayward and defender Nic Newman are in line to replace Robinson, with the recently upgraded Shaun Edwards and rookie Robbie Fox also sure to be looked at.

Jarrad McVeigh (calf) and Isaac Heeney (glandular fever) are no chance to return, while Longmire said small forward Tom Papley (knee) needs some time in the reserves before he can press his case for a senior call-up, after an interrupted pre-season.