High five: Johnston and Walker combine to demolish Roosters

It was Walker's night, with three try assists, two tries and two line breaks in a commanding performance to which the Roosters had simply no answers.

"Cody's got great instincts, that's what he plays with and what makes great football players. Nothing has to be structured for him," said Rabbitohs coach Wayne Bennett.

"He's had some great games for us… it was up there with his best."

The game started well for the Tricolours with Josh Morris powering over in just the fourth minute and he would have had a try assist shortly after when backing up a James Tedesco half break but his offload floated forward.

Despite the no-try, the Rabbitohs looked to be on the rack and struggling to get out of their end until some individual brilliance from Cody Walker turned the tide.

The in-form five-eighth made a clean break from inside his own half in the 14th minute then backed up to finish off a long-range team try, then with his side quickly back on the attack fired a pass for Johnston to break the line and score with some help from Bayley Sironen and suddenly Souths were up 12-4.

They looked to have their third when Campbell Graham took on a short side and crashed over but the Bunker believed there was a tiny bobble in the act of grounding and ruled no try.

It didn't slow the Rabbitohs down for long as Johnston carved over for his 100th career try then Graham belatedly got a deserved try backing up a Corey Allan clean break and kick ahead to make it 24-4 just past the half-hour mark.

With Souths attacking yet again in the shadows of half time, Luke Keary tackled Mark Nicholls before he received a pass.

The ball bounced off Keary's shoulder into the Roosters in-goal with Nicholls chasing through to ground it. The play was sent up 'no try' due to a perceived knock-on from Nicholls with the Bunker ruling there was insufficient evidence to overturn the decision.

Souths had to settle with two points for the penalty for an off-the-ball tackle and a commanding 26-4 half-time advantage.

Walker sent his team further in front 10 minutes after the resumption, offloading for Allan to score before the Roosters clawed one back when Daniel Tupou touched down off a Keary grubber.

Souths hit back immediately through that man Walker again, who produced a perfectly-timed chase from a Reynolds attacking kick to bag his second try.

Cameron Murray got his name on the scoresheet with a scrappy try, touching down after a Reynolds grubber bounced off a few players then broke the line the very next set for who else but Walker to set up Johnston's hat-trick.

The team went the length from the next set with Allan unselfishly finishing in the in-goal and handing the ball back to Johnston for his fourth with the Rabbitohs remarkably going the length once again in the next set with Johnston carving over in the corner.

It was the second time Johnston has bagged five tries in a match - the previous coming in 2017.

It that wasn't enough to the Papua New Guinea international, he also moved into first place on the leading try-scorer list, one ahead of Cowboys winger Kyle Feldt.

The result means the Rabbitohs will host Newcastle at ANZ Stadium in the first week of the finals.

The Roosters will slip to fourth if the Eels beat Wests Tigers after their worst loss of the Trent Robinson era and their biggest score conceded since 2010.