Penrith’s magic number has emerged after making NRL history with a record-equalling 17-straight wins to make their first grand final in 17 years with a 20-16 victory over South Sydney.

In a tough preliminary final at ANZ Stadium, the Panthers kept the Rabbitohs at arm’s length in front of a crowd of 30,116 – the biggest NRL attendance in Sydney this season.

Saturday’s match was the third preliminary final in a row for Souths, coming away empty handed on each occasion.

The Panthers led 14-6 at halftime and managed to hold on as star halves Cody Walker and Adam Reynolds tried all they could to keep the Rabbitohs alive.

Red hot five-eighth Walker produced one of the plays of the season with seven minutes remaining, shooting a ball to the left edge for Corey Allen who toed it through to score.

Barely able to run after copping a leg injury at the start of the half, Allen brushed away celebrations with teammates as he buckled in pain.

It was a brave performance for the Souths fullback who had a nervy night at the back.

But the Panthers had done their homework on Wayne Bennett’s men and defended bravely.

Halfback Nathan Cleary continued his remarkable form with the boot, setting up two tries from kicks for Brian To’o and Tyrone May in the first half.

The first was to draw level with Souths in the eighth minute when he put up a bomb that Alex Johnston couldn’t wrangle, knocking on for To’o to clean up and score.

A set play under the posts with a short kick for May to pounce on put the Panthers in the lead in the 28th minute, where they stayed until the end.

Second-rower Isaah Yeo also starred, breaking through the middle of the field to set fullback Dylan Edwards up for the game-sealing try in the 67th minute.

Earlier, livewire Panthers hooker Api Koroisau was taken from the field with a shoulder injury after making a tackle on Reynolds.

He was taken up the tunnel but returned after getting a painkilling shot and is not expected to be in doubt for Sunday’s grand final against Melbourne.

However, there will be concerns for prop James Fisher Harris after he was put on report for a high shot midway through the first half.

The Panthers are set to welcome back second-rower Viliame Kikau from suspension for the decider at ANZ Stadium.

Penrith’s 17th win in a row is an NRL-era record – matching Canterbury’s run in 2002 before they were stripped of all their points for salary cap breaches.