George Gregan says Australia will have to dominate at the breakdown against New Zealand if they are to triumph in an "epic" Rugby World Cup final on Saturday.

For the first time in World Cup history, the final will be contested between the two southern hemisphere rivals.

Defending champions New Zealand are the favourites to retain their title, having displayed pace and power throughout their line-up as well as an ability to dominate in the pack.

But Gregan - a World Cup winner with Australia in 1999 - is confident that the Wallabies, who beat New Zealand in the Rugby Championship earlier this year, can upset the odds.

"It's an epic final, the two best teams are in the final. Consistency of play has demanded it. It's the first time they've faced off in a World Cup final and it's exciting," Gregan told Omnisport at a Land Rover event.

"What Australia need to do is put in their best possible performance. To beat New Zealand you have to beat them in areas they're good at.

"One of those is the breakdown. You have to beat their forwards at the tackle contest. If you do that, you go a long way to providing ball for your team to operate and score points.

"You need a lot of points against New Zealand. They score points from anywhere and you have to do it for 80 minutes because they come at you from everywhere."

Gregan is predicting that the most crucial battle could come at fly-half with All Blacks great Dan Carter - considered by many as the best 10 of all time - coming up against Bernard Foley, who has been one of the standout performers at the World Cup.

"Both are very good running players and choose moments when to run. They have good instincts," Gregan added. 

"You saw it with Foley against England, and against France with Dan Carter. He [Carter] has good footwork at the contact. He may not have the speed he had as a younger man but enough to get through the break.

"Foley is the same, they can break the line then offload, they pick their moments very well. It's going to be really important, because you get limited chances when you play against New Zealand and Australia as a fly-half because defences and the breakdown is so good.

"But both players' natural instincts are very good and it will undoubtedly have an impact on the game."