The job is not done for Fremantle.
They will need to win at least two of their last four home-and-away games to have a chance of playing in the finals, and three of four to make sure they seal the deal.
And the Fremantle Football Club has come up one game short of September often enough to know that such deals are rarely sealed after round 18.
The Dockers only needed to beat bottom team Melbourne in round 22 of 1997 but with a badly banged- up team they didn't get close.
In 2004, they lost the last four games of the season to finish on 11 wins, one win and 1.8 per cent from 8th spot.
And in 2005, just a week after Justin Longmuir had taken a clutch mark and kicked an after-the-siren goal against St Kilda to keep their season alive, they fell away badly after half-time against Port Adelaide in Adelaide.
But Saturday's western derby victory against West Coast marked an important landmark for this Fremantle team and coach Ross Lyon.
This was not the strongest Eagles team to take the field this season.
West Coast's injuries have been exacting an increasing toll on their form as the season has progressed.
But that shouldn't detract from a Fremantle performance that looked more like the sort of pressure football to sustain the Dockers under any circumstances than any brand the team has played in a 17-year history - and that includes the preliminary finalists of 2006 and the young semifinalists of 2010.
This was not about the element of surprise, all-out attack or youthful exuberance.
Rather it was about the elements of persistence and hard-nosed discipline, of what Lyon would term "playing both sides of the ball".
The Dockers hammered away relentlessly at the Eagles for 2 1/2 quarters, stifling their scoring and smothering their creators.
Then, when the Eagles' resistance lapsed, the Dockers kicked four goals in 10 minutes late in the third term to kill the game off.
Here was the balance between defence and attack Lyon has craved all year.
Here was a glimpse of the Sydney premiership team that Lyon had been such an integral part of and the St Kilda side he nearly took to a flag in 2009 and 2010; the ability to change gears when a game either demanded you close it down or offered you the chance to open it up.
After a great first-up win at home against Geelong in round one, the Dockers had managed such football for 2 1/2 quarters against Sydney in round two, and for three quarters against Adelaide in round 10 and Essendon in round 13.
But bad lapses in all those games and a complete second-half collapse against the Eagles in round nine saw the Dockers carry a 1-6 record against top-eight teams going into the derby and questionable credibility as genuine finals contenders.
They took a significant step towards enhancing that credibility on Saturday afternoon.
The fifth-placed Eagles were vulnerable, but we should not forget that the Dockers have been without Aaron Sandilands for more than two months, Anthony Morabito for the season, Greg Broughton for the past three weeks and, until two weeks ago, had been without Nat Fyfe for three months.
Many would have rated Sandilands as Fremantle's most important player before the start of the season. Fyfe is their best young player and Morabito is the youngster we want to see play again.
Broughton is no one's idea of a superstar, but he did finish third in the club's 2011 best and fairest. He is no one's idea of a mug.
When a coach takes the reins under the sort of circumstances that saw Lyon succeed Mark Harvey, there will be inevitable scrutiny and scepticism.
That scepticism has been voiced, but you suspect the Dockers' hierarchy will feel comfortable about the decision after the latest derby.
Lyon is due to be given some credit.
He was a proven coach when he arrived but he has been an agent for change at Fremantle and much of the change has been for the better: Matthew Pavlich back to attack, Clancee Pearce's career transformed, Michael Walters delivered the tough love that may save his.
The Dockers aren't there yet, but they are getting there.
And while it has taken some time for tangible evidence to emerge, Lyon is a good chance to take them there.