Sydney midfielder Ollie Florent has failed to make the distance with a kick from 50m on the final siren to hand Port Adelaide a dramatic two-point triumph at the SCG.
The Power had snatched the lead less than two minutes earlier when forward Jeremy Finlayson slotted a set shot with a snap on the way to a 9.12 (66) to 9.10 (64) victory on Saturday night.
Finlayson finished with a game-high three goals as the Power kicked four of the last five majors in a remarkable turnaround after trailing by as much as 20 points early in the final term.
The Swans looked to be cruising to a brave win halfway through the final term despite having their defensive pillars Paddy and Tom McCartin both subbed out before halftime due to head knocks.
But goals to Todd Marshall, Connor Rozee, Jed McEntee and then Finlayson shook up the pulsating contest and gave the Power an important second win of the season.
Zac Butters (27 disposals, one goal) and Xavier Duursma (22) battled hard for the Power, while Rozee overcame a slow start to finish with 20 touches and a crucial goal.
It was a cruel outcome for Florent who had been outstanding for the Swans with 33 disposals and an earlier goal, while Chad Warner had also led the resistance when the Power first surged either side of halftime.
Warner finished with 30 touches (19 contested) and two goals, while Luke Parker (22) and Callum Mills (21) were also influential.
The Swans (2-2) will also be sweating on the health of Paddy McCartin after he knocked his head on the ground, then had to be helped from the field and subbed out early in the opening term.
The former No.1 draft pick has revived his career since joining the Swans as a key defender last year, after his five seasons with St Kilda were marred by eight concussions.
Paddy's younger brother Tom was also concussed when diving for a loose ball and colliding with a Power opponent just before the main break to leave the Swans without their defensive pillars.
Peter Ladhams booted the opening goal and played through the match without major incident after being suspended for a gut punch on Wines the first time he faced his former side last year.
Both teams head to South Australia next for the inaugural Gather Round with Sydney facing Richmond on Friday night, while Port Adelaide host Western Bulldogs on Saturday night.
