A booming 78th-minute field goal to Dragons centre Patrick Herbert gave his side a crucial 25-24 win over the Roosters at Allianz Stadium on Sunday.
The result has massive finals implications with the Dragons moving into fourth spot on the Holden Cup ladder while the Tricolours missed a golden opportunity to return to the top two.
The early exchanges had all the hallmarks of a finals match with both sides throwing plenty at each other in an absorbing back-and-forth feeling-out period.
Having survived a close call at the other end of the field, the Dragons opened the scoring in the 14th minute with skipper Patrick Herbert charging onto an out-ball from Matt Dufty.
The lead lasted barely 10 minutes as wrecking ball Reuben Porter blasted his way through the defensive line to get the Roosters on the board before Kiah Cooper ran a perfect line from the next set to make it 12-4.
Not to be outdone, the Dragons showed they can be equally adept at hitting holes when winger Izaac Thompson timed his run to perfection to go over untouched, before halfback Jack Payne did it all himself to give the Red V a narrow 14-12 advantage at the break.
The lead quickly ballooned out to eight points when Jai Field backed up a huge break by No.9 Reece Robson to score minutes into the second half, only for the Roosters to immediately hit back through winger Bernard Lewis.
With the game in the balance, Thompson cut back against the grain to cross for his second, but Field missed the relatively easy conversion that would have given the Dragons some much needed breathing space.
The missed kick would come back to haunt the visitors as Jackson Hastings toed through a grubber from halves partner Lachlan Lam to level the scores with eight minutes left to play.
With a top-four finish on the line, both teams traded long-range field goal attempts before Patrick Herbert of all people stepped up and struck a monstrous 40-metre effort as purely as you would like to seal the upset win.
Dragons 25 (Izaac Thompson 2, Patrick Herbert, Jack Payne, Jai Field tries; Jai Field 2 goals; Patrick Herbert field goal) defeated Roosters 24 (Reuben Porter, Kiah Cooper, Bernard Lewis, Jackson Hastings tries; Jackson Hastings 4 goals) at Allianz Stadium. Half-time: 14-12 Dragons.