Harry Rowston had just one goal in 15 games before Saturday, when he booted four for the Giants in a 17.9 (111) to 11.10 (76) win at People First Stadium.
Victory would have likely meant an end to the Suns' 15-year wait for a finals campaign.
And they looked likely after stalling the Giants' fast start in the second term.
But with the Giants chasing their own finals-clinching victory, it was the visitors who tore clear behind supreme pressure and devastatingly accurate set-shot kicking.
Rowston's haul, Max Gruzewski's three majors and three other multiple goal-kickers ensured the Giants weren't exposed by the absence of injured spearheads Jesse Hogan and Jake Stringer.
The win was the Giants' sixth straight against their expansion rivals and 15th from their past 16 encounters.
It almost certainly locks in their finals berth - the Giants' third straight under Adam Kingsley - and keeps their top-four hopes alive.
The Suns' September plans remain in pencil. They likely still need at least one win from their final-round double-header - against Port Adelaide and Essendon - to play in their first post-season since their 2011 admission.
The Suns had tidied up defensively, matched the Giants' pressure and clawed their way back from a 20-point deficit to trail by just four when Ben Ainsworth chipped through his set shot.
But it all swung after a remonstrating Ben Long gave away a 50m penalty in the goal square for remonstrating over a free kick.
The ball popped out the back at the other end and Darcy Jones ran into an open goal.
Aaron Cadman won a free kick minutes later and the Giants had their third in the final four minutes of the half when 21-year-old Rowston marked and goaled after the siren.
The margin, suddenly out to 22, stretched further with Rowston's fourth to begin the third term.
Ben King's first kick of the game - midway through the third term - was pure and briefly breathed some life into the Suns.
But again the Giants ran away from the bounce and replied through Gruzewski.
Goals to Jake Ricciardi and Toby Bedford, awarded a free kick when officials felt Alex Davies was taking on a tackle, all but sealed the result with time left in the third term.
Finn Callaghan led the Giants' midfield, while Suns star Matt Rowell was well held.
The lead swelled to 45 points and shaped as a potentially damaging percentage blow to the Suns, before they kicked three late goals.
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