Gregan refused to take anything away from the Wallabies' three comprehensive victories over England and Ireland last month, but conceded the level of competition is set to rise.
"The Tri-Nations is a step up from the Test matches we have played," he said.
"That is not to denigrate the matches we have played but we are fully aware that these matches are a step up in intensity, and the ball is in play a lot longer.
"But it is going to take a really strong effort because New Zealand-Australia games are always competitive right through to the 80th minute."
Like Australia, New Zealand won each of their three lead-up Tests last month, but coach Graham Henry has made no secret of the fact he used those matches against Ireland and Argentina to experiment ahead of both the Tri-Nations and next year's World Cup.
Ireland nearly broke a 100-year drought against the All Blacks in both their clashes, and Argentina pushed an almost entirely different squad right to the edge.
But Wallabies lock Dan Vickerman feels the All Blacks used those matches well and he is under no illusions about the task ahead in Christchurch.
"The Kiwis have done a lot of work on their line-out, against Ireland they had three good jumpers," he said.
"Introducing Jason Eaton into the line-out is going to help them a lot."
The 33-Test veteran is confident the Wallabies can get the better of their arch-rivals but conceded they will have to be at their best at all times.
"We've got to have that pack mentality and play as a pack," he added.
"In Test match rugby you have got to do well in your set-pieces and around the field, and give your backs good quality ball, and that is certainly an area we are going to look to do well in.
"The All Blacks always look to make it tough for you in that area and if we are not on our game we will be made to pay pretty dearly."