'As good as you'll see': Johnston goes top of class at finishing school

"That third try he got was quite remarkable. He had to adjust the ball on the way to the try-line, while he had all that stuff going on in his head, knowing what he had to do to get the ball down.

"The first one he scored it looked like the rest of them were on the treadmill. He just outpaced them with his speed."

The Rabbitohs were far from their best against a depleted Knights outfit but never looked seriously threatened with Cody Walker and Adam Reynolds laying the platform for Johnston to cash in.

Bennett turned to rookie hooker Peter Mamouzelos as a replacement for Damien Cook, who along with Cameron Murray was rested following Origin I.

Bennett might've regretted not doing the same with fullback Latrell Mitchell, who showed clear signs of fatigue throughout the match after his stirring effort for the Blues on Wednesday. 

"I was pleased with him, I thought it was a great effort by him and he probably would've scored two tries if he wasn't as tired as he physically was," Bennett said. "His second half was really good."

The Rabbitohs looked in for a comfortable night when Johnston strolled over the line for his first untouched after two minutes but the top-four side were made to work for their win.

A 57 percent completion rate after 40 minutes was met with a hint of complacency from the home team with the Knights regularly gifted handy field position.

A line break from Bradman Best ended in pain for the Knights centre, who provided a quick pass for Dom Young to score his first NRL try but later left the field with an ankle injury.

Young's effort in the corner was undone minutes later when the Rabbitohs generated momentum after Jacob Saifiti was placed on report for high contact on Liam Knight.

Newcastle's right-edge defence failed to regroup with Walker finding Johnston on the edge for his double.

South Sydney's complacent efforts were continuing throughout the opening 40 minutes, however, with a Campbell Graham error enabling the visitors to bounce back after points.

Newcastle's mid-year recruit Jake Clifford looked far more comfortable in his second appearance for the Novocastrians to control the Knights in attack.

Clifford placed the ball on a dime for Kurt Mann to pounce on a Johnston error near the line to narrow the Rabbitohs' lead to 12-10 going into the break.

"I liked everybody's effort in 'D'," Bennett said.

"To their credit they've been working on their defence. They understand they can't get beaten by 50 points like we did [against Penrith and Melbourne], if we want to be a good team.

"They got the rewards tonight because defence won them the game."

The loss of Best three minutes after half-time sent the Rabbitohs down the right edge in attack with Young repelling two try-scoring opportunities with attempted intercepts to save points.

There was no such success on the left edge, however, with Walker sending Johnston over for a third to extend the lead to eight.

The Bunnies put the exclamation mark on their 10th win of the season when Reynolds put in a deft kick for Jaydn Su'A to kick again and touch down.