They say defence wins NRL premierships, and that might prove to be true this weekend with two preliminary finals set to determine who goes into the grand final.

The first preliminary final will see the South Sydney Rabbitohs face the Manly Sea Eagles on Friday evening, before the favourite for the grand final clash is forced a week earlier by Penrith's loss to Souths in the Week 1 qualifying final as the Panthers take on the Melbourne Storm.

Both preliminary finals will be played at Suncorp Stadium in Brisbane, with the entire competition moved north after the COVID outbreak in Sydney, Melbourne and Canberra.

It's been a difficult season dominated by high scorelines, but now the four best defensive outfits remain and it could decide the competition. These could be important stats for you to use online betting sites in predicting the winner.

South Sydney Rabbitohs vs Manly Sea Eagles

This will be the more free-flowing game of the weekend, with the Rabbitohs and Sea Eagles both having the ability to put points on in a hurry.

They are at the bottom of the top-four when it comes to defending, but still ahead of most of the rest of the competition.

The Rabbitohs have a slightly better record than their opponents, having conceded 39 less points throughout the course of the season.

They have been far better during the second half of the competition too, muscling up in the qualifying final against the Panthers a fortnight ago to limit the dangerous Penrith attack.

Manly were clubbed by Melbourne in their own qualifying final, but have been strong defensively, with Melbourne the only team to put more than 20 on them since Round 21.

Still, with a week's rest and an already better record than their opposition, you'd have to assume the Rabbitohs have the defensive edge for the first preliminary final.

Melbourne Storm vs Penrith Panthers

For the first 12 rounds of the season, the Panthers went on an undefeated run where they conceded less than ten points per game. It seemed they would be simply unstoppable come finals time with no one able to breach the line.

That has tailed away in the second half of the season though to the point where the Storm have almost caught the Panthers for thebest defensive record in the competition.

They have conceded just 30 more points than the Panthers to the end of the regular season and continued that outstanding form in their qualifying final over Manly.

The Panthers have a brilliant up and in style of defence, but could struggle to hold out the Storm, as they did last time the teams met.

This will be a battle for the ages in a replay of last year's grand final, but the Storm, based on recent form, seem to have the edge defensively at least. If that translates to attack, then they will not only take the victory, but outright favouritism heading into the grand final as the competition's best team.