West Coast will enter the penultimate round and a mouthwatering showdown against rampaging Richmond with its top-two destiny in its own hands after shaking off a brave Adelaide by 10 points on Sunday.
But the Crows' hopes of September action have taken another hit, and they will have to come from outside the finals spots over the last two games to feature in the post-season.
Don Pyke's men arrived armed with a plan to stifle the Eagles at Optus Stadium, maintaining possession through careful ball movement, and it kept the reigning premiers within touching distance for most of the contest.
But conceding a mountain of inside 50s (63-41) was always risky and the dam wall burst during the third term, when the home side piled on five goals to two to establish a match-defining lead.
West Coast ultimately ran out 13.12 (90) to 12.8 (80) winners, with star forward Jack Darling drilling three goals and midfield bull Elliot Yeo (25 disposals) living up to his growing reputation as one of the AFL's truly elite players.
The Crows were gutsy and trailed by a single point at half-time, thanks largely to young gun Darcy Fogarty booting three of his five goals, recalled ruck Sam Jacobs' efforts in his first game since round two and Daniel Talia's blanket job on Josh Kennedy.
Teenager Fogarty was superb in just his second match this season, proving the focal point while Taylor Walker (two goals) fought an engrossing battle against Will Schofield.
But they were dealt a cruel blow at the opening bounce of the third quarter when Rory Sloane was collected by friendly fire from star Matt Crouch (43 disposals), which ended the co-captain's game due to blurred vision.
It was the catalyst for West Coast's engine room to get on top and burst of four unanswered majors proved decisive.
Their 15th victory didn’t come easy, but the Eagles moved level again with ladder leaders Geelong and Brisbane on points, setting up a massive round 22 when the top-four teams will all go head to head.
While the Eagles dropped to third due to Brisbane's thumping win over Gold Coast, the Lions have to play ladder leaders Geelong next round and West Coast can earn a home qualifying final by going undefeated.
The Crows have tumbled from fourth to ninth after losing five of their past seven, and will spend the week outside the eight for the first time since round six, with clashes against Collingwood and the Western Bulldogs to come in a tense finale.
West Coast: Brad Sheppard copped a heavy hit from Matt Crouch in the opening minutes and took plenty of time to get to his feet before playing out the game.
Adelaide: Taylor Walker needed his ankle re-strapped in the second term but was on shortly after. Adelaide's other skipper Rory Sloane needed to come to the bench after some friendly fire at the opening centre bounce of the second half and couldn't come back on due to blurred vision.
The Eagles travel to the MCG for the match of the home and away season against Richmond with massive implications for the top four, while the Crows need to beat the battling Magpies or their September dream could be on life support.
WEST COAST 3.4 6.6 11.9 13.12 (90)
ADELAIDE 1.4 6.5 8.5 12.8 (80)
West Coast: Darling 3, Allen 3, Waterman 3, Ryan, Rioli, Sheed, Kennedy
Adelaide: Fogarty 5, Walker 2, Murphy, Sloane, B.Crouch, Betts, Knight
West Coast: Yeo, Darling, Gaff, Rioli, Sheed, Shuey
Adelaide: Fogarty, M.Crouch, Talia, B.Crouch, Jacobs, Laird
West Coast: Nil
Adelaide: Sloane (eye)
Umpires: O'Gorman, Meredith, Fleer
Official crowd: 54,994 at Optus Stadium