Coach Jason Demetriou concedes South Sydney are at risk of missing the NRL finals unless they can snap the form slump that continued with a 31-6 loss to resurgent North Queensland.
The Rabbitohs have now conceded an average of almost 33 points in their past five games and are inside the top eight on point differential alone, despite sitting atop the ladder after 11 rounds.
They missed the spark of injured fullback Latrell Mitchell at Accor Stadium on Sunday and could not bounce back after the Cowboys neutralised danger man Cody Walker.
With just one victory from their past five starts, Demetriou said the Rabbitohs urgently needed to break back into the winners circle.
"If we wait any longer, we won't be in the finals. It's as simple as that," he said.
"We've done a great job to put ourselves in a position to have a crack at this competition.
"But unless we get back on the horse and get back to being the Rabbitohs that we have been to start the first 11 or 12 rounds, we'll be in some trouble."
Souths' defence was their saving grace in a 5-0 first half but the Cowboys opened them up at will in the 10 minutes after the break.
Valentine Holmes, one of five Cowboys backing up from State of Origin, scored in back-to-back sets after Scott Drinkwater and Jeremiah Nanai line breaks in raids that proved decisive.
Drinkwater and Holmes were stand-outs for the Cowboys, whose 2-5 start to the season is now a distant memory.
Having beaten heavyweights Melbourne, Penrith and Souths in their past three matches, the Cowboys are within striking distance of the top eight.
"Where we sat on the ladder, it just gave us no alternative," Cowboys coach Todd Payten said of his side's win.
"It's great for our confidence and belief. I've got to give a rap to our Origin boys that backed up - we don't win if they don't back up.
"Tommy Dearden and Drinky had really strong games for us as well."
Souths will need more from Walker while Mitchell sits out with his calf injury for at least the next two games but Demetriou refused to blame the fullback's absence for the loss.
"Latrell's a world-class player," Demetriou said.
"We miss him, there's no doubt about that, but he doesn't stop six tries.
"We've got to step up, we've got to deal with that. He's not there."
Walker kicked the ball dead twice in the first 10 minutes and when his cut-out pass sailed past Alex Johnston and into touch, the Cowboys were in position to open the scoring after 31 minutes.
As if to taunt his opposite number, Cowboys five-eighth Tom Dearden sent winger Murray Taulagi over with the same cut-out pass play Walker had been attempting.
Like his halves partner, Souths halfback Lachlan Ilias struggled to rouse the Rabbitohs but did get his side on the board from a scrum play in the 58th minute.
The game was out of Souths' reach when rookie teenager Kulikefu Finefeuiaki broke the line and crossed under the posts - another beneficiary of Drinkwater's ball-playing.
The win was the Cowboys' first against South Sydney since 2017, breaking a seven-game losing streak against them.
Cowboys co-captain Jason Taumalolo missed the game with a hamstring issue but is expected to return to face Wests Tigers next week.
