In a battle of teams tipped to fight for the wooden spoon, the Giants poured in five supergoals in the second term alone and seven overall to turn a one-point quarter-time deficit into a remarkable 58-point lead at the main break.
From there it was all GWS, with All Australian Jeremy Cameron kicking four goals and one supergoal in a 7.11.10 (139) to 0.10.11 (71) annihilation of a terribly disappointing St Kilda outfit.
Dylan Shiel kicked three supergoals of his own, while Tom Bugg, Adam Treloar, Curtly Hampton and Rhys Palmer all stood out for a Giants side that had winners all over the ground.
With Josh Hunt, Heath Shaw, Shane Mumford and Dylan Addison providing some welcome balance to their young list, the Giants look a far more dangerous prospect heading into 2014.
"It's just good reward for the boys to know that if they work hard, bring the effort and the energy, they can stay in games," GWS coach Leon Cameron said afterwards.
"We got some lucky bounces in the second quarter with some of those nine-pointers, but it is a reward for hard work.
"The (NAB Challenge) game against the Swans last week, they punished us when we made some fundamental errors.
"We were probably a little bit better at that than St Kilda today."
Both sides were fielding relatively strong line-ups and the result leaves new Saints coach Alan Richardson with plenty of work to do before the season gets underway.
Richardson was disappointed with the effort, particularly in the second quarter, but wasn't dropping his head two weeks out from the new season.
"We certainly didn't kick the ball well, didn't use the ball well and didn't work hard enough to make the kicks a little bit easier," he said.
"Their pressure was really good and that was the disappointing part, particularly in the second quarter, that we didn't cope with that pressure.
"We'll make sure we work on that really strongly."
The coach also said Lenny Hayes had got through the game well, following an early television suggestion he had tweaked a hamstring.
Nick Riewoldt kicked two first-quarter goals and Jarryn Geary and Jimmy Webster had their moments, but it was otherwise a poor showing from the Saints, who face Port Adelaide in their final hitout next weekend.
An apparent hamstring injury to Lenny Hayes only added further injury to insult for a St Kilda side already missing best and fairest winner Jack Steven for the next two months with a broken foot.
In a town that produced footballing royalty in Wayne Carey and Paul Kelly, it was modern day heroes Riewoldt and Cameron who got their respective sides underway in the first quarter.
Riewoldt got the opening goal on the board in the second minute of the game courtesy of a free kick against GWS co-captain Phil Davis, a scenario that would repeat itself at the end of the term.
The Giants and Saints get better acquainted during a brief skirmish in Wagga Wagga. Picture: AFL Media
Cameron also kicked two goals in the first quarter, getting the better of a tight duel with James Gwilt, as the Giants took a one-point lead into the first break.
While the first term was an arm wrestle, the second was an absolute avalanche, starting with a supergoal and a goal from a fresh looking Jonathon Patton.
Nick Haynes, Dylan Shiel, Will Hoskin-Elliott and Cameron all got in on the supergoal action as GWS tore the game wide open.
The Giants missed some opportunities in the third quarter, but still managed to stretch the lead to 68 points before romping home in the final term.
WHAT WE LEARNED
NEW FACES
Greater Western Sydney: For a 19-year-old playing his first senior game, Josh Kelly was far from overawed and showed some good hands and a calm approach. Jed Lamb was dangerous around the half-forward line, while Dylan Addison spent time at either ends of the ground.
St Kilda: First-round draft picks Jack Billings and Luke Dunstan were given an opportunity against the Giants. Dunstan managed to pick up 22 touches and kick a goal, but it was a tough night for Billings. Former Brisbane Lion Billy Longer, who has added some muscle to his frame, had some good moments in the ruck.
St Kilda: Riewoldt, Geary, Webster, Montagna
INJURIES
Greater Western Sydney: Coniglio (concussion)
St Kilda: Nil
SUBSTITUTES
Greater Western Sydney: Townsend replaced Coniglio at quarter time; Plowman replaced Mumford in the final term.
St Kilda: Schneider replaced Billings at quarter-time; Ross replaced Delaney in the second term; Delaney replaced Gwilt in the third term.
Reports: Townsend (GWS) reported for high contact on Armitage in the fourth quarter.
Umpires: Stevic, Jeffery, Lehner, Pawley
Official crowd: 7,944 at Robertson Oval
Twitter: @AFL_JD