West Coast have used the return of Ben Cousins as a springboard for one of their most important wins of the season, beating arch-rivals Sydney by 12 points in another classic at Subiaco Oval.

In a script no-one would dared written, Cousins was magnificent in his comeback, racking up 38 possessions in his first game of football since his suspension four months ago.

And after a month of indifferent form which culminated in a 91-point humiliation by Port Adelaide last week, Cousins' emotional return sparked the Eagles back into form, allowing the premiers to run out 16.16 (112) to 15.10 (100) winners.

As important as Cousins was to West Coast, Ashley Hansen's recovery from injury also boosted their firepower, with four goals adding to three from the impressive Brent Staker and the brilliant Dean Cox.

And with Barry Hall out with a groin injury, Ryan O'Keefe was the unlikely spearhead, his four goals keeping a dogged Swans in the contest.

The visitors were dealt a massive double blow before the bouncedown, with Hall and Tadhg Kennelly both late withdrawals after a week of fitness speculation.

In contrast, Chris Judd took his place for West Coast despite a lingering groin injury, and of course Cousins was included after his self-inflicted exile.

The superstar started on the bench in his first top-flight game since last year's grand final, and was a spectator when O'Keefe kicked his first inside two minutes.

From there, though, the six-time All Australian looked like he had never been away.

Racking up 20 possessions in the first half, the plan to play Cousins for around 80 minutes flew out of the window, as he kept finding space and the ball.

Eagles coach John Worsfold tried his utmost to downplay Cousins' dream comeback.

"We selected him knowing he was fit to play, and that is pretty much it," Worsfold said.

"We picked him to play, and play well for the team. I am proud of our footy club with the way we have helped him, and certainly proud of the effort he put in to get himself right."

He also said he anticipated Cousins would pull up well in time to play the Western Bulldogs, in six days, at Telstra Dome.

"If there is (such a thing as second up syndrome) it is for weak people, to have an excuse not to play well second up because a lot of players play well second up."

Even Sydney coach Paul Roos dipped his lid to Cousins.

"He played alright yeah," the Swans coach said with a chuckle. "But I can't worry about him now, thankfully."

"Ben has played against us in every game bar round one at Telstra Stadium, so that was not an issue for us.

"Every one knew at some point he would come back into the team, so that was probably common knowledge.

The Swans coach said although both teams were not in top form, they still produced another great spectacle.

"Some ball use (for) both sides was probably a bit unlike the games we have had ... but above all it was a really high standard game, and hopefully we can take some confidence out of that."

Leo Barry's apparent hamstring strain in the second term did nothing for Sydney's cause, forcing Paul Roos to throw Heath Grundy back and Barry forward.

And with weight of numbers and possessions putting West Coast in charge, the usual slender margin blew out alarmingly in West Coast's favour after half-time.

Adam Hunter re-established a ten-point lead and then Brent Staker and Cox marked and goaled, with the ruckman's shimmy past Jolly appearing to have ended the contest.

With the lead up to 41 points after six minutes of the last term following Hansen's fourth goal, the fairytale appeared complete - but Sydney had not read the final chapter.

In true Bloods style, they refused to lay down, reducing the deficit to 12 with six fourth-quarter majors - before time ended their comeback and ensured a happy conclusion for Cousins.

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