Sydney veteran Ryan O'Keefe suspects St Kilda coach Ross Lyon may be playing mind games with his decision to drop Michael Gardiner for Saturday night's AFL elimination final at Etihad Stadium.

Lyon opted to axe Gardiner on Thursday night, five days after praising his work in the Saints' last-start 20-point win over Carlton.

Swans ruckman Shane Mumford was best afield when the two teams met in round 22, dominating the stoppages and out muscling Saints counterpart Ben McEvoy to tally 52 hitouts.

Many were expecting Lyon would keep Gardiner in the side after playing the first game of an injury-wreaked season against the Blues, to help combat Mumford's burly frame.

The Saints instead promoted David Armitage at the expense of the former West Coast ruckman.

However Gardiner has been named as an emergency and O'Keefe smells a ruse from Lyon, a former Swans' assistant coach.

"I know Ross is pretty clever. I think he'll probably throw a few curve balls at us," O'Keefe said on Friday.

"I think there will be a few late changes. He'll mix it up a bit. We'll just have to wait and see.

"It's going to be a crucial battle throughout the night (at the stoppages).

"It's going to be a grind right to the end.

"Both teams play hard, physical footy and finals-like footy and that's the way it's going to be. We expect an exciting but tough battle."

O'Keefe is expecting revenge to be a factor for St Kilda after the Swans' 15-point win at ANZ Stadium.

"We definitely expect them to be better with the inclusions of (Zac) Dawson and (Justin) Koschitzke, they're a really good side," he said.

"They're a proud side, so obviously they don't take their losses lying down and I think they're going to come back for some revenge.

"It's going to be a fierce battle."

The Swans will be without Heath Grundy, who was diagnosed with glandular fever on Thursday, but O'Keefe says the inclusion of premiership player Lewis Roberts-Thomson will soften the blow.

"He (Roberts-Thomson) is a proven, established player who can play various roles - forward or back.

"I know it's a big loss to lose Reg but it's a bonus for us that we can get Lewie to slot in."

Gardiner was substituted out in the third quarter against the Blues, with Lyon saying after the game he would be a useful player to have against Mumford.

"I thought he was really good in the centre bounces and his spread. We all know Sydney's ruck work is their strength so that gives us an option there for sure," Lyon said after the game.

"I thought he was really good - he's a very talented player."

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