Bontempelli was outstanding as the Bulldogs overran their opponents with five unanswered goals in the final quarter of their 15.10 (100) to 12.10 (82) victory at Marvel Stadium on Friday night.
Inspirational captain Bontempelli racked up 38 disposals, 10 clearances and two goals as the Bulldogs squared their season ledger at 6-6 in pursuit of a finals berth.
But the win came at a cost, with James Harmes and Laitham Vandermeer added to a growing injury list when they were both struck down by hamstring trouble before halftime.
Furthermore, Sam Darcy and Taylor Duryea are facing scrutiny from the match review officer.
Darcy was involved in a huge late collision with Brayden Maynard early on, cannoning into his opponent's back after the Magpie defender claimed a mark, while Duryea made high contact with Nick Daicos off the ball.
Lachlan McNeil (C) and Jamarra Ugle-Hagan (R) led up front as the Bulldogs upset Collingwood. (Joel Carrett/AAP PHOTOS)
Darcy gave away two 50m penalties in the opening term but responded well, finishing with a team-high three goals.
In-form ball-winner Adam Treloar (37 disposals, 11 clearances, one goal), Bailey Dale (35 touches) and Jack Macrae (19 possessions, two goals) were also important for the Bulldogs, while Lachlan McNeil and Jamarra Ugle-Hagan added two majors each.
After a week of speculation around his playing future, recalled ruck-forward Rory Lobb hit the post twice and finished with 1.2, including the crucial first goal of the last quarter from a free kick.
Brownlow Medal favourite Nick Daicos was outstanding for Collingwood with 32 disposals, two goals and a club-record 16 clearances, surpassing the previous mark of 15 set by Nathan Buckley in 1998.
Josh Daicos (23 touches, two goals) and Jack Crisp (24 disposals) were busy, while former Fremantle forward Lachie Schultz kicked three goals in his best return for the Magpies so far.
The fuse was lit early when Darcy crashed into Maynard under a high ball, sparking a melee as Collingwood players rushed to remonstrate with the Bulldogs youngster.
Maynard goaled from the resulting 50m penalty and Darcy gave away another in a separate incident moments later, but was let off the hook when Jack Crisp missed his shot.
Sam Darcy was a key for the Bulldogs, with a big early hit on Brayden Maynard and three goals. (Joel Carrett/AAP PHOTOS)
The Magpies led by as much as 22 points in the early stages and on the balance of play should have been further in front than their 5.7 to 3.2 advantage at quarter-time.
They were made to pay as the Bulldogs kicked the first four goals of the second term and briefly hit the front before halftime.
The Dogs dominated territory in the second quarter with a 21-6 inside-50 advantage but Collingwood kicked three goals from their limited opportunities and led by three points at the main break.
Nick Daicos's silky skills stood out in the third term as the Magpies inched two goals clear by the final change, but it was all Bulldogs in the final term.
Rhylee West put them in front and Bontempelli gave his side breathing space before the Dogs ran away with the important result.
It was Collingwood's first defeat since round two.
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