The Dockers had been labelled premiership pretenders after losing five of their first seven games, but Saturday's 16.10 (106) to 11.11 (77) victory at Optus Stadium had the 45,811-strong crowd daring to dream.
Dominant ruckman Sean Darcy and onballers Caleb Serong and Andrew Brayshaw led the way as the hosts ran over the reigning premiers with speed and intensity.
Yet to taste premiership success, Fremantle spent six seasons on the September sidelines before making the finals last year, bowing out with a semi-final loss to Collingwood.
Supporters raised their expectations during the off-season when the Dockers acquired talented former Melbourne ruckman Luke Jackson, whose recent return to form has mirrored that of his new club.
Fremantle's third straight win - and by far their biggest this season - lifts them to ninth on the ladder ahead of another huge clash with Melbourne at the MCG next Saturday.
And Longmuir can see his charges growing in confidence after dominating at the stoppages, albeit against a Geelong midfield missing Patrick Dangerfield and Mitch Duncan.
"We were probably caught up (earlier in the season) in, whether it was the expectation or a bit of fear," he said.
"Now we're playing with freedom, and that goes for stoppage (too).
"We're worrying about what we can control, not what we can't ... they're just playing on more instinct and we're getting after the ball and getting after the (opposition)."
Midfield coach and ex-Geelong premiership player Joel Corey had been pivotal in helping to devise strategies with the input of players, Longmuir said.
Young star Andrew Brayshaw's leadership was again on display against the Cats, finishing with 33 disposals, 10 tackles and a goal.
Nat Fyfe, who lined up for his first start since round one after an injury absence and two cameos as the substitute, rotated between the midfield and forward line and gathered 17 disposals before being benched in the third period.
Longmuir hailed the two-time Brownlow Medallist as "instrumental" early in that term as the Dockers piled on three straight goals to extend their lead.
"We left him on for a little bit longer than we probably anticipated but it won't hurt him in the long run," Longmuir said.
"He was really open to coming off when he did and getting fresh legs through the middle of the ground."
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