Having led the NRL for most of the season, the Sharks are now hovering precariously above the top two trapdoor following the 12-6 defeat, only a win clear of the rampant Raiders with two rounds to play. It means Canberra are likely to leapfrog Cronulla into the top two and a home qualifying final with a game against the Wests Tigers to follow Sunday's clash with battling Manly.

Second-placed Cronulla meanwhile play the rejuvenated Roosters on Saturday, before heading south to play ladder-leading Melbourne in the final round. Canberra now boast a superior for and against record.

Cronulla's slump started with a golden-point stalemate against Gold Coast four rounds back which halted a club-record 15-game winning run. Since then they've lost to Canberra, St George Illawarra and now Souths.

Any plans the Sharks had to arrest their untimely form slip took a hefty blow before kick-off with captain Paul Gallen ruled out for a second straight week, nursing a calf injury. Gallen told Triple M before the game that he couldn't afford to risk aggravating the injury ahead of the finals.

"I had a good run today and even this afternoon told the trainer I thought I could play but they just said it's too big a risk," Gallen said. "We've put ourselves in a good position, we don't need to take unnecessary risks and we've only got a five-day turnaround. It got pretty good by last Friday, but the session I did today I had to do last Friday and I just didn't have the confidence to do it."

Monday's rainy ANZ Stadium where Souths had struggled all season, winning just two games prior to this match, looked the perfect venue for the Shire men to grind their way back into form. But it was the Rabbitohs who bossed the middle of the ground for large parts of the game in front of 7588 hardy souls.

Souths halfback Adam Reynolds went off with concussion 15 minutes from half-time, never to return, but the Rabbitohs didn't lose their spark.

In a dour struggle, five-eighth Cody Walker broke the deadlock 33 minutes in after taking a harmless looking offload from Nathan Brown before shaking off some shoddy defence 10 metres out and scoring next to the posts.

Damien Cook converted, then made it 8-0 right on half-time thanks to a penalty goal.

Five minutes after half-time, Cronulla had a try disallowed when Michael Ennis grounded the ball but was found to have done so after illegally stripping it from Sam Burgess. The Sharks took control soon after and started relentlessly pounding the Rabbitohs line, Wade Graham eventually crashing through to score despite Jason Clark's best efforts to hold him up.

The visitors kept pressing for most of the half, but a bruised Rabbitohs defence held stiff before English import Joe Burgess scored acrobatically on full-time to seal the win