SYDNEY tall forward Sam Reid is in major doubt to play next Saturday's Grand Final against Geelong after being subbed out with an adductor injury in the Swans' thrilling win over Collingwood.

Reid suffered the injury in the second quarter of the one-point triumph and despite having treatment at half-time, failed to return to the field and was replaced by youngster Braeden Campbell.

Sydney coach John Longmire was tight-lipped post-match, giving little indication of the 30-year-old's prospects of facing the Cats.

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"We don't know yet," Longmire said.

"It's just after our game. I don't deal in the 'what ifs' an hour after the game. Let's just wait and see."

Reid has been an instrumental cog in the Swans' wheel in the second half of the season and was again having a big influence at the SCG, kicking a first-quarter goal and having five score involvements from his six first-half disposals.

Despite his absence Sydney was able to grind out the narrowest of wins, holding off a rampant fourth-quarter comeback from Collingwood.

It completed a remarkable rise from the Swans, who spent 2019 and 2020 in the bottom four, before being bundled out in an elimination final last year by crosstown rivals Greater Western Sydney.

Despite undergoing a semi rebuild a few years ago – and introducing a host of young talent that is now the bedrock of the current team – Longmire said he was always confident the Swans would rebound quickly.

"We had high expectations internally," he said.

"We want to give these blokes a crack at playing finals every year, that's our role as the footy department … and to give your supporters hope.

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"Last year we were disappointed to get bundled out in the first week.

"This year we've just had confidence in our playing group. They've got some experience there, some terrific young blokes that I really enjoy working with.

"We have an opportunity this week, but we've got to make the right decisions on game day and get ourselves ready to go."

Longmire was full of praise for elder statesmen Luke Parker and Lance Franklin for their respective impacts on the win.

Parker ran with red-hot Magpie Jordan De Goey most of the day, keeping him to just 12 disposals while gathering 23 himself, while Franklin bounced back from a quiet night against Melbourne in the qualifying final to kick two goals in an influential performance.

Longmire acknowledged Geelong's impressive runaway victory against Brisbane on Friday night, but said his team could get better ahead of next week's decider.

"I thought we got a lot right tonight, I thought sone of our defensive work was pretty good," he said.

"We probably mucked up a few opportunities when we had the ball going forward, but we come out of the night knowing we did a lot right.

"We'll have to play at our best (next week). We'll give it a go."