AUCKLAND, NEW ZEALAND - JUNE 19: NRL great Andrew Johns looks on prior to the round 15 NRL match between the New Zealand Warriors and the Sydney Roosters at Mt Smart Stadium on June 19, 2016 in Auckland, New Zealand. (Photo by Anthony Au-Yeung/Getty Images)

The South Sydney Rabbitohs have managed to make it past the Sydney Roosters and Cronulla Sharks in the first two weeks of the finals, but have been warned a far tougher tests awaits them this weekend.

The win over the Sharks - who have been bounced out of the finals in straight sets - means the men from Redfern will now play the Panthers in a preliminary final for a spot in the grand final on Saturday evening.

The rematch between last year's grand finalists comes as something of a surprise with the Rabbitohs originally finishing seventh on table, and they will be up against it with Thomas Burgess suspended, and injury clouds hanging over Siliva Havili, Alex Johnston and Jai Arrow, all of whom failed to finish the game against the Sharks at Moore Park.

Their attack struggled throughout the game despite running on 36 points, with the Sharks unable to capitalise on errors, and former Newcastle Knights, New South Wales Blues and Australian Kangaroos legend Andrew Johns, speaking on The Sunday Footy Show, said that they will need to be far better to challenge the Panthers.

"They need to improve so much on (their performance against the Sharks) if they're going to beat Penrith," Johns said.

"Made a lot of errors.

"Freddy spoke about to beat Penrith you're going to have to use ball movement.

"Jason Demetriou spoke after the game ... he said they're going to have to chase the game.

"But if they make errors early coming out of trouble, Penrith will just suffocate them."

The preliminary final will kick-off at 7:50pm (AEST) on Saturday, held at Accor Stadium in Homebush.