Fremantle midfielder David Mundy says the heartbreaking loss to Geelong in round 20 was the night Freo realised they were back to their best.

Mundy was a central figure in that match as his shot after the siren drifted just right of the goalpost to hand the Cats a narrow two-point win.

But since then Fremantle have produced three quality victories against Hawthorn, the Brisbane Lions and Port Adelaide to secure fourth place and the double chance in finals.

Fremantle will travel to Sydney to take on the Swans in a qualifying final at ANZ Stadium on Saturday afternoon.

Mundy said the team has gained a lot of confidence from the three wins but he stressed Freo can't rest on their laurels.

"I think since Geelong, that's when we really felt like it's started to click and every aspect of our game seems to be going well," Mundy told afl.com.au.

"But it's not something we can just sit back and rely on now. We've got to keep on the front foot and keep pushing."

The veteran midfielder overcame a quiet first half against Port Adelaide to gather 13 touches and five clearances in the second half to help set-up the eight-point on Saturday that confirmed Freo's top-four finish.

"It's very important," Mundy said.

"History says you've got to be in the top four and we've put in a lot of hard yards over the last few years and this year specifically we've really dug in right from the start and we feel like we've earned this chance.

"To come to the last game and have it within our power and then to win it is really good.

"It's a credit to the boys. I thought they really stuck it out today. Hopefully we'll reload and go again next week."