The Fijian phenomenon took a towering mark over a huge pack with 30 seconds to go and calmly slotted a goal after the siren to send a packed Patersons Stadium into pandemonium, giving West Coast an extraordinary two-point win over North Melbourne, 12.18 (90) to 13.10 (88).
Five talking points: West Coast v North Melbourne
The game looked to have slipped through the Eagles’ fingers thanks to their inaccuracy in front of goal, which plagued them in losses to Carlton and Port Adelaide earlier this season.
The Kangaroos led by 15 points at the 11-minute mark of the last quarter when Brent Harvey kicked his second of the night.
Josh Hill's third goal of the second half cut the margin to eight points.
Sam Wright had a chance to bury the game with three minutes left, but hit the post with a check-side from the pocket, giving the Eagles a glimmer of hope.
West Coast went the length of the ground and Luke Shuey took an uncontested mark 20 metres out, and converted to cut the margin back to four.
Adam Selwood received a questionable free kick on the wing with 40 seconds left to provide the Eagles with one last opportunity, and Naitanui did the rest.
"I backed him to mark it, and kick a goal," Eagles coach John Worsfold said after his side evened its win-loss ledger at 4-4 with a third consecutive victory.
"It happened so quick.
"Just looking at the clock, it was just kick it in long. Nic was the one we were probably thinking might be able to mark it, and somehow he did it."
The final siren sounded as Naitanui went back to take his kick, and the Eagle ruckman took to Twitter after the game to admit he had been nervous.
To put it bluntly, that siren tightened my cheeks right up haha #welldoneglassynscoot— Nic Naitanui (@RealNaitanui) May 17, 2013
Click here to vote for the three best West Coast players from the game
The Kangaroos, who led at every change, silenced the crowd early with their highest-scoring opening term at Patersons Stadium, kicking 6.1 in the first quarter.
Daniel Wells was electric with 10 disposals for the quarter, and his ball use was particularly damaging. North Melbourne had 22 inside 50s to nine and West Coast was unable to rebound from defence.
Click here to vote for the three best North Melbourne players from the game
But the Kangaroos could never put the game away, falling to 3-5 for the season. They have become the first side since Fitzroy in 1978 to lose three games by under a goal in the first eight rounds of a season.
"It's pretty gut-wrenching, obviously," North coach Brad Scott said after the match, refusing to blame the umpires for the loss despite showing his displeasure with several decisions late in the contest.
"It's obviously bitterly disappointing to lose from that position, but we didn't close it out.
"We were never able at any point of the game to put it beyond doubt, even though we probably kept them at arm's length, but we couldn't break the margin any further than that."
The crowd only had to wait 22 minutes for a showdown in the centre circle between the headline attractions, Majak Daw and Naitanui. Daw won the opening exchange with a longer reach, Naitanui the next with a bigger leap.
But Daw's night ended in the third term when he was subbed out for the fourth time in his five-game career, having had four disposals and a goal.
The Eagles worked their way back after quarter-time, but could not take advantage of their opportunities. They also suffered some key injuries during the match.
Sharrod Wellingham was subbed out of the game in the second term with a left ankle problem. He will have an MRI after x-rays cleared him of bone damage.
The former Collingwood onballer was just three games into his first season with his new club after missing the opening five games with a right ankle injury from a trampolining accident.
Will Schofield, who shadowed Daw when he was deep in attack, left the game during the third term with a compound dislocation of a finger. He came back in the last quarter but struggled to use his left hand. Worsfold confirmed he will have surgery to repair the damage.
Scott Thompson was reported for an off the ball incident which left Matt Rosa winded in the second term.
A free kick paid in favour of Adam Selwood was a hot topic after West Coast's win. Picture: AFL Media
WEST COAST 3.2 4.9 8.14 12.18 (90)
NORTH MELBOURNE 6.1 7.4 10.6 13.10 (88)
West Coast: Hill 3, Kennedy 2, Shuey 2, Cox, Darling, LeCras, Masten, Naitanui
North Melbourne: Black 3, Harvey 2, Wright, Wells, Thompson, Petrie, Cunnington, Daw, Ziebell, Swallow
West Coast: Glass, Naitanui, Hurn, Priddis, S.Selwood, Gaff
North Melbourne: Harvey, Wells, Black, Cunnington, Mullett, Goldstein
West Coast: Wellingham (left ankle), Schofield (finger)
North Melbourne: Nil
West Coast: Brad Sheppard replaced Sharrod Wellingham during the second quarter
North Melbourne: Sam Gibson replaced Majak Daw during the third quarter
Reports: Scott Thompson (North Melbourne) for striking against Matt Rosa (West Coast) in the second quarter.
Umpires: Dalgleish, Nicholls, Meredith
Official crowd: 38,146 at Patersons Stadium