It's a big day for injured Swans Jarrad McVeigh, Callum Mills and Aliir Aliir on Wednesday, with the trio having to get through a closed training session to prove their fitness for Saturday's Grand Final.

Uncertainty surrounds the availability of McVeigh (calf), Mills (hamstring) and Aliir (knee) and much of their selection hopes will depend on how they pull up on Thursday after a searching session on Wednesday.

Swans assistant coach Stuart Dew admitted on Wednesday morning the coaching staff remained "in the dark" about whether the players would be fit to play. 

"They need to go 100 per cent (on Wednesday)," he said on SEN radio. 

"If it was round four you might leave it to the last minute and not really require them to go 100 per cent, but I think given the enormity (of the occasion), you really want to be settled. 

"They'll either be right or they won’t.”

Mills strained his right hamstring in the Swans' qualifying final loss to Greater Western Sydney on September 10.

Should the NAB AFL Rising Star winner be deemed fit to play against the Western Bulldogs at the MCG he will have been out for 21 days.

McVeigh hobbled off the following week in the Swans' semi-final win over Adelaide. The co-captain failed to come up for the Swans' impressive preliminary final win against Geelong, but appears a real chance to return.

Aliir suffered a minor medial ligament strain in Friday night's win over Geelong, but coach John Longmire said earlier in the week the key defender was progressing well after the Swans had grave fears his season was over.

The defender joined in handball drills on Monday but did not do any running.

The Bulldogs also have some selection issues of their own, with Matt Suckling (Achilles) and Jordan Roughead (eye) still no certainties to play.

The two-time premiership player with Hawthorn missed the Bulldogs' thrilling preliminary final win over Greater Western Sydney after his Achilles issue emerged in the wake of the semi-final win over his former club. 

Roughead, who was hit in the face by the ball in the preliminary final, is firming to take his place in the side after spending the early part of his week in a dark room to ease the pressure on the bleeding in his eye.

The ruckman did not train on Tuesday but the Dogs are optimistic that he will play.

Midfielder Lin Jong did his chances of a recall no harm after a best on ground performance in Footscray's 31-point VFL premiership triumph over the Casey Scorpions at Etihad Stadium last Sunday.

Returning from a broken right collarbone in the Dogs' elimination final against West Coast, which looked to have ended his season when he required surgery, Jong collected 29 disposals, six inside 50s and four clearances.

The Norm Goss medallist looks to be an outside chance of returning to the team.