SHATTERED coach John Longmire has taken ownership for Sydney's 81-point Grand Final hiding to Geelong on Saturday, saying he let the entire club down.

Conceding his decision to select injured Sam Reid was a mistake, a forlorn Longmire said physically and mentally the Swans were never in the hunt.

Reid injured his adductor in the preliminary final win over Collingwood seven days earlier and lasted until just before half-time against the Cats before being subbed off with a recurrence of the same problem.

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"We were obviously confident, that's why we picked him, but we made a mistake," Longmire said.

"Personally, you feel like you've let a lot of people down.

"You let your players down, you let your supporters down, you let your staff down, you let your board down. That's how you feel."

Longmire said it was evident his team was overwhelmed by the magnitude of the occasion, trailing by 35 points at quarter-time and never making inroads.

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He said the performance was as foreign as anything he'd seen this season.

In fact, it was Sydney's heaviest defeat since losing to Hawthorn by 89 points in round 16, 2015.

"No aspect of the game looked like the way we wanted to play and we hardly got anything right, from the selection of Sam to the way the game looked, we just didn't get it right," Longmire said.

"Normally we give our supporters what I think is pretty good value for money, and physically, mentally we just didn't give ourselves a chance to do that.

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"They had 12 players 29 and over, it was an experienced, hardened team as you'll come up against and they handled it that way.

"We didn't. we didn't have our heads in the game from the very start. We weren't able to think clearly or perform at that level we should have."

Longmire said once he had given the result some distance, he would recognise 2022 for all the positives it had provided his team.

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Just two years ago the Swans were in the bottom four, jumping to an elimination final last season and into this year's decider.

"It's a bit hard at the moment, in the shadows of that defeat, to think clearly enough to reflect on the season," he said.

"That'll come in time I guess, but it'll take a bit of time to get over.

"I'm confident in that playing group, they're a really good group.

"We've had some wonderful achievements and taken some real steps forward as a footy team. Most our players would have improved this year.

"We just buggered it up today."