Daniel Vettori admits plugging the gap created by Jacob Oram's absence will be a difficult task for New Zealand.

Oram has been ruled out of the upcoming two-Test series in Australia, starting in Brisbane on November 20, with a lower back problem that forced him home early from the Black Caps' tour of Bangladesh.

"Jacob is a huge loss. In my opinion he's our best player and our most important player," Vettori said.

"When you take him out of the line-up it makes it hard for Braces (coach John Bracewell) and myself to select the side (because it affects the) balance. But also you just take quality out of your team.

"It's a tough ask to replace him but hopefully by the time the West Indies come round he'll be fit and raring to go."

The Black Caps skipper has put his hand up to fill Oram's number seven batting role and is unconcerned about taking on the extra responsibility as New Zealand go in search of their first Test series win in Australia since 1985.

"My theory on captaincy is that you lead with your performance so I'm putting myself in those positions where I give myself the most opportunities," the left-arm spinner explained.

"Batting at seven and doing the majority of the bowling is the best way to do that and I'm looking forward to it. There's no harder place to do that than in Australia so hopefully I can."

Despite the fact Australia have struggled against India in recent weeks, particularly in the second Test which they lost by 320 runs, Vettori expects them to bounce back strongly on home soil.

"I still look at the Australian team as the number one side in the world, particularly in their own conditions," he said.

"They are going to come back pretty strong. They've got an exceptional batting line up. I think Australian teams always tend to produce good batting line-ups. Maybe where they've struggled a little bit is in the lack of a quality spinner and in a place like India you always get found with that.

"In Australia you may not need it as much but I still see them as the toughest ask in world cricket."