South Sydney will not play in the NRL finals, falling to a 26-12 defeat at the hands of bitter rivals the Sydney Roosters, who kept their finals hopes alive as virtual sudden-death football arrived a week early at Sydney's Olympic Stadium.

Corey Allan and Cam Murray exchanged scores in a tight and tense first half before the Roosters hit the front shortly before half time through an acrobatic Fetalaiga Pauga score.

James Tedesco extended that lead but Michael Chee Kam hit back for the Bunnies to set up a grandstand final stanza.

However, the Roosters withstood a tremendous amount of pressure defensively before Billy Smith and Sam Walker's tries sealed the tricolours' fifth win in a row. 

The Rabbitohs were tackled 31 times inside the Rooters 20 and dominated the middle portion of the second half, but could only score twice as their season slipped away.

The Roosters are not guaranteed finals football — they need Penrith to beat North Queensland and see Cronulla beat Canberra to sneak in — but having been 14th as recently as a month ago, to be in the conversation come season's end is some achievement.

For the Rabbitohs though, who through 11 rounds were leading the competition and considered premiership favourites, missing out on finals is an enormous blow.

"It's hard, I'm not gunna lie," Souths coach Jason Demetriou said post-match.

"From where we got to, the pre-season we had, the first half a season, yeah, disappointing.

"The performance probably summed up our back end of the year, we're just not quite nailing a few things. Our effort, our fight was outstanding, but just not capitalising on opportunities and then leaking points."

He added that there will be a "deep review" into what went wrong in the back end of the season, but that he was responsible as head coach.

Souths suffered a disrupted fortnight, losing assistant coach Sam Burgess amidst reports of training ground unrest.

Demetriou said the speculation was "disappointing that things are getting out" but was only "a small part of lots of little things," that contributed to the overall capitation.

"It's hard to put your finger on where it went wrong," Rabbitohs skipper Murray said.

"I don't have all the answers.

The Roosters bucked their recent trend of going behind early by scoring first, Allan dotted down after seven minutes when Souths failed to diffuse a Sam Walker bomb.

The Rabbitohs lost fullback Blake Taaffe midway through the first half after he copped a knee to the head in a tackle, the 24-year-old failing his HIA to be ruled out of the contest.

However, soon after, Cam Murray burst through to score South Sydney's first try, smashing through a gap to finish a spell of Rabbitohs pressure.

Joseph Sua'ali'i scored a penalty goal to level the scores, but there was little else to separate the sides in a bruising first half have gave credence to the billing that finals had come early.

Both teams were flying into tackles and relished hitting their opposite numbers back — never more so than when Izaac Thompson laid out Billy Smith with a monstrous hit that dislodged the ball, prompting as much celebration as either of the first two scores.

The Roosters took the lead again just before half time though, Sam Walker passing wide to Pauga, who acrobatically put down in mid air under pressure from Lachlan Ilias.

After half time, the Roosters extended their lead thanks to a miraculous score from Tedesco.

Keary crabbed across field on the half way line, double pumping and then passing wide to a flying Pauga, who raced down the left sideline before finding Tedesco, who still had plenty to do 10 metres out from the line, but still burrowed his way past three Rabbitohs defenders to score.

A successful challenge from Campbell Graham for a knock on by the Roosters under their own posts proved a masterstroke, as Cody Walker sprung a trap down the left side and Chee Kam did the rest — his first try for the Rabbitohs, having shifted from the second row to centre after Taaffe's injury.

That try started a run of extraordinary pressure on the Roosters line, but it held firm and the Roosters, having weathered the storm, made the Rabbitohs pay.

Luke Keary got to the outside of Ilias to put the Rabbitohs on the back foot, with Smith scoring after fending off Graham and bursting through Alex Johnston to put the Roosters up by eight with eight to play.

Walker then sealed the win, gathering his own chip-kick through, sparking a small brawl as South Sydney's composure evaporated, along with their season hopes.

In Friday's opening game, Manly-Warringah ended their season with a dominant 54-12 victory against the Wests Tigers at Brookvale Oval.

Tolutau Koula scored inside the opening 60 seconds from Manly's first set and, although Api Koroisau levelled for the Tigers, the Sea Eagles were never in doubt of securing the two competition points.

Koula added a second, followed by a double from Jason Saab and Ethan Bullamore's first try of the season to lead 26-6 at half time.

Haumole Olakau-atu scored after the break, before Daly Cherry-Evans handed Jake Trbojevic a try on his 200th NRL appearance with a pass in the in-goal after he scythed through the line.

Raymond Tuaimalo Vaega, Gordon Chan Kum Tong and Cherry-Evans all scored as the Sea Eagles turned on the style to run in 10 tries.

"A great crowd turned up considering we couldn't make finals and we really tried to respect that," Trbojevic told ABC Sport.

"We put in a really good performance which was nice and hopefully give us a bit of confidence for next year."