Heading into the final round of the season last weekend, it seemed unlikely Perth would break its 23-year finals drought.

The Demons needed to beat the previously undefeated South Fremantle, and for reigning premiers Subiaco to lose to third-place West Perth.

Delahunty said the side knew it was a difficult proposition heading into Saturday's contest.

But at three-quarter time, with Perth trailing South Fremantle by 10 points, the news came through that Subiaco had lost, opening the door for the Demons.

"I think there were about an extra 1000 supporters who showed up to the game once Subi lost," Delahunty said.

"It gave us a lot of extra motivation, knowing our fate was in our hands.

"Last year, the boys lost by three points to miss out on finals by percentage, so I think that was in the back of their minds."

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The extra motivation propelled Perth to a dominant last quarter.

Only inaccurate goalkicking kept the match close, as Perth booted 1.8 while keeping South Freo scoreless in the last term to win by 5 points, 8.18 (66) to 9.7 (61).

"It was a super last quarter. It was just about as good as we have played this year," Delahunty said.

"It would have been handy if we had have kicked straight, but it was just super to be a part of.

"The scenes after the game, I haven't witnessed anything like that before, just for making finals. For some of the supporters, it felt like they'd won a grand final.

"It was nice to be able to contribute to the club and get something of a reward."

The victory against the minor premiers has given Perth some serious momentum heading into a three-week finals campaign.

They play West Perth in an elimination final on Sunday at 3.35pm AEST time.

"There's certainly a lot of confidence that we can be competitive this finals series," Delahunty said.

"We've knocked off the top two sides now, and we only lost to West Perth by a goal last time, when we were four goals up at one stage.

"We're optimistic, but we're not going to get too far ahead of ourselves."

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