Sydney gave itself a massive chance of winning back-to-back AFL premierships by beating West Coast by one point in another thrilling qualifying final at Subiaco Oval.

The Swans earned the week's rest and a home preliminary final after rallying to get in front of the Eagles and then withstanding several challenges before winning 13.7 (85) to 12.12 (84) before a sell-out crowd of 43,116.

In the fourth-straight game between these sides decided by four points or less, the Swans' win earned them a home preliminary final and next weekend off.

The vital break will give co-captain Barry Hall and fellow forward Michael O'Loughlin a much-needed rest after the duo booted nine goals between them in Herculean performances given they were injured during the match.

Hall booted five goals - including one late in the game to restore his side's lead - despite struggling with back or hip soreness, while O'Loughlin kicked four majors including the eventual winner despite carrying a groin injury.

O'Loughlin ran into an open goal at the 26-minute mark after Eagle Drew Banfield failed to clear the area with an attempted spoil, and the Swans dug deep to hold on to their precious lead.

Sydney's win was its first at Subiaco since 2001 and avenged the heart-breaking losses to the Eagles in last year's qualifying final and the round 15 clash this season.

But if West Coast is to avenge last year's grand final loss to Sydney, it must win via a semi-final against the winner of Sunday's Collingwood-Western Bulldogs clash.

Fremantle's loss to Adelaide means both Perth teams will host semi-finals next weekend.

In a titanic final term alone, the lead changed six times as both sides traded blows and the match continued into an extraordinary intensity.

Ben Cousins put the Eagles up with a brilliant snap, Chris Judd did the same and then Eagles rover Steven Armstrong - from a Dean Cox tap - again put the home side in front.

But Sydney responded on all three occasions, through Adam Schneider, Hall and finally O'Loughlin.

Sydney rallied from two goals down early in the game and led by 22 points early in the third quarter.

But West Coast again responded and two huge goals from Quinten Lynch, plus Judd's ability to go up a gear turned the game the Eagles' way.

Judd won the points in his duel with fellow Brownlow medallist Adam Goodes, but the Swans were efficient through the ground with precise kicking.

For Sydney, Jarrad McVeigh did a good job on Cousins, while Malceski, Kirk, backman Ted Richards and forward flanker Ryan O'Keefe were good.

Rowan Jones was good for the Eagles, along with Dean Cox and half-back David Wirrpanda.

Sydney coach Paul Roos said the Swans' quest to win consecutive flags was a lot more comfortable after the victory.

"I thought in the last five minutes we probably looked a little bit fresher, which was encouraging because in the past two games they have just steamrollered us, and we have been hanging on," Roos said.

"The significance is you are already in the preliminary final - that is the only difference ... (we are) not necessarily (better placed), but I must admit I am sitting here a lot more comfortably now than I was after the game last year.

"But I didn't know what was to come last year, and I don't know what is to come now.

"But am I happier now than what I was after last year's game? - absolutely."

West Coast coach John Worsfold said he was both proud of his side's effort, but disappointed.

"If we had of won the game I would have been satisfied with our performance. We're just disappointed," he said.

"If we had of won by a point I would feel like Paul Roos feels. If they had lost, he would feel like I feel."

Worsfold said his side gave away some bad free kicks through bad tackles in the first half, but disputed a suggestion the Swans' forward line worked better.

"If we had of been up by one point at the end would our forward line have been more efficient?" he said.

Worsfold said he had told his players to focus on freshening up for next week's semi-final and was confident they could bounce back.

"I've got all faith in our players that they're good enough to take on and beat any side," he said.

Forward Ashley Hansen, midfielder Daniel Kerr and winger Andrew Embley are available for next week after recovering from injury, while Worsfold was confident Daniel Chick would recover from a kick to the shin.

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