Brad Fittler will be banking on his interchange to turn the screw and guide NSW to victory in Wednesday's Origin decider.

The battle of the bench will be critical to the outcome of State of Origin III after the interchange proved the decisive factor in the series' opening two games.

Fast middles helped Queensland to an early advantage in Origin I before the NSW big men punished the Maroons in Origin II in the second half in Perth.

It sets up an intriguing plot line to how Wednesday's decider at Suncorp Stadium will be won, particularly given Brad Fittler's NSW side will be without marathon man Payne Haas.

Haas' spot in the starting side has been filled by Junior Paulo with debutant Jacob Saifiti tasked with bringing the grunt off a bench that includes hooker Damien Cook, Angus Crichton and utility Siosifa Talakai.

"I think all the bench know their job," Fittler said. "We changed things up (after game one).

"That's the plan. Normally if their teammates can help them with different things in the game it sort of works out."

With Haas out, Fittler conceded he may deploy Talakai differently after conserving the Cronulla big man for a 17-minute stint in game two when NSW were already assured of victory.

"It ended up being between 'Sifa' and Jack (Wighton for the No. 17 role) which tells you what sort of respect we have for 'Sifa'," Fittler said.

"It probably depends how the game goes and I'm sure there'll be a few curlies tossed up and he (Talakai) is the player who can fill most roles."

The real curly one for the Blues is whether Queensland will start debutant Tom Dearden at five-eighth or opt to move Ben Hunt to the No. 6 berth following the omission of Cameron Munster.

Fittler is unsure but has been given an insight into Dearden's ticker by the playmaker's North Queensland teammates Reece Robson and Chad Townsend, who make up the extended NSW squad.

"It'll be either him or Ben Hunt sitting on that left hand side," he said.

"We do our homework on all the players and obviously Tommy's a little bit younger and newer.

"One thing they (the Blues' Cowboys players) have been telling us is how much they like playing with him and they say he's a tough little kid who puts his head in places where most don't."