Young phenom Logan Morris kicked eight goals as the Lions claimed a 25.9 (153) to 15.6 (96) win in front of 66,846 fans at the MCG on Friday.
"Happy to win, happy to get the double chance," coach Chris Fagan said.
"When we were 6-6, sort of halfway through the season, finishing where we have didn't quite seem possible.
"It's been a great effort by everybody at the club to knuckle down and put ourselves in this position. I don't know if we'll finish 3rd or 4th, but I think 4th is as bad as we can finish, isn't it?
"You fight all year to try and give yourself the best chance to win a flag and you've got to finish in the top four, I reckon, to do that."
Collingwood coach Craig McRae opted not to rest any stars, then had Pendlebury (knee bursa) ruled out in the second quarter.
Pendlebury appears in doubt for the wildcard match against either the Western Bulldogs or Carlton.
"My understanding is we had some precautionary action around tightness in the back of his knee and which might be hamstring related," McRae said.
"But it's on the minor side and if there's something there, a scan will show that."
Magpie defender Dan Houston should be OK after a dislocated finger.
Brisbane (64 points) sit third and will stay there unless Hawthorn (60) hammer West Coast by 90 or more, with Melbourne (60) too far back on percentage to catch the Lions.
Brisbane led by 75 points midway through the final quarter then gave up six straight goals - a percentage hit - before steadying.
The team that finishes third will avoid facing minor premiers Fremantle in Perth and instead take on a decimated and embattled Sydney at the SCG.
The Swans are without Isaac Heeney, Chad Warner, Nick Blakey, Riley Bice and James Jordon, who were suspended for the rest of the season for "breaching club standards".
Those five players are linked to a police investigation into allegations of sexual assault at East Melbourne's Pullman Hotel on Monday morning.
Brisbane will have next week off before finals.
On return from suspension, Brisbane defender Ty Gallop appears certain to face match review scrutiny for a dangerous tackle on Charlie West - though the Magpie forward played on.
Veteran Dayne Zorko could be looked at for catching Jack Crisp high with an attempted fourth-quarter.
Morris was unstoppable in a performance Fagan labelled "special" and "exceptional".
Irishman Conor McKenna kicked four majors, including one where he smothered the ball then brilliantly toe-poked through a freak goal from a tight angle.
"What's the prize for the goal of the year? I reckon he's won it, hasn't he? I'm calling it now," Fagan said with a grin.
Oscar Allen jagged four goals, Eric Hipwood kicked three, and Lachie Neale (16 clearances, 35 disposals) and Josh Dunkley (27 disposals) shone.
Collingwood's Jordan De Goey (32 disposals, six clearances, two goals) was superb.
Nick Daicos (26 disposals) and Darcy Cameron were rested late, while Sam Swadling (32 possessions) was excellent.
Brisbane led by 22 points at halftime then exploded, with the contest over by three-quarter time.
"I don't think we'll watch any of this," McRae said.
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