The last spot in the NRL Grand Final is up for grabs tonight when the table-topping Penrith Panthers host the South Sydney Rabbitohs in Sydney.

The winner will face the Melbourne Storm on October 25 in the decider, who were sensational in the first preliminary final of the weekend against the Canberra Raiders.

Frank Endacott told D'Arcy Waldegrave the success of the Panthers, who are on a 16-game winning run, is not down to luck.

"They're doing everything right, I think they're going to miss their big back-rower Viliame Kikau.

"I think at home you have to go with Penrith, but I wouldn't count Souths at all."

Kick-off between the Panthers and Rabbitohs is at 9:50pm.