The Rabbitohs' preliminary final against the Sea Eagles at Lang Park on Friday will be the fourth time in a row they've reached the preliminary final stage as they look to break through for their first NRL grand final since 2014.

They've stumbled at the penultimate hurdle three years in a row, but are looking to turn that around in coach Wayne Bennett and captain Adam Reynolds' final season at the club.

Nicholls said they were a different group to the past three seasons.

"We haven't really spoken about it too much internally - I guess everyone's aware of it so there's no need to address it," he said.

"But we definitely spoke about it in pre-season and we're a different group.

"We know what the prize is at the end of the day ... I guess it's motivation for us."

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One of the crucial things the Rabbitohs need to do to get there will be to shut down Trbojevic.

He's Manly's superstar and one of the favourites to win this year's Dally M Medal.

The Melbourne Storm successfully kept him quiet in the qualifying final and Nicholls said they would look to replicate that by minimising "Turbo's" influence.

Nicholls said he and his fellow forwards had a role to play by shutting down the Manly fullback's time and space.

"We've got to kick long and get down there in one line - we've got to do it together is the key," he said.

"And as a fullback he pops up all over the place so we're going to have to be good on the kick chase, we're going to have to contain their back three and get up in line speed and get into their forwards.

"He can poke up in the middle and end up out on the edges so it's going to be important to have a good, solid defensive line working together for the whole 80 minutes."

Nicholls has agreed to terms on a two-year extension to remain in cardinal and myrtle, with just a transitional role for life after football for the NRL to ratify.

The 31-year-old has finally established himself at Souths, after stints at the Canberra Raiders and Storm where he played just 28 games across six seasons before finding his way to the Bunnies.

But he's racked up 80 games in four years with the Rabbitohs and established himself as a starting prop this season.

Remarkably, he's only started one NRL game before this year before securing the role.

"It's always nice to get your future sorted and not have to worry about those things, especially coming into the end of the season and the bigger games," Nicholls said.

NRL PRELIMINARY FINAL

Friday: South Sydney Rabbitohs v Manly Sea Eagles at Lang Park, 7.50pm.