Steve Hansen backs Beauden Barrett against Wallabies

Richie Mo'unga's form won't be enough to stop Beauden Barrett from wearing the All Blacks five-eighth jersey against the Wallabies.

Deafened by a growing clamour for Super Rugby star Mo'unga to wear No.10 in this month's twin Bledisloe Cup Tests, coach Steve Hansen has delivered a reality check.

While Hansen was impressed by the 24-year-old's brilliant performances for the champion Crusaders, he won't go past two-time world player of the year Barrett in Sydney on August 18.

Barrett's form was steady in the June series whitewash of France and modest over the closing weeks for the sub-par Hurricanes, but Hansen has pointed out that Mo'unga played behind a dominant Crusaders pack.

The veteran coach has built his international success on selection loyalty, pointing to the misguided demand in New Zealand for five-eighth Dan Carter to be dropped before his starring role at the 2015 World Cup.

"We have to build slowly with Richie and build his experience, but in the meantime we have got a player in Beauden who has been the best player in the world for the last two years. We won't be in any rush to shift him," Hansen said.

"Both of them are very good players.

"Our job is to maximise the talent we've got. Over time, you will see Richie get more test matches, I'm sure.

"But I think about a bloke prior to the [2015] World Cup we went to and everyone wanted us to drop Dan Carter, but he had one ingredient that the other blokes didn't have, and that was experience."

Mo'unga isn't even likely to be the backup to 64-Test veteran Barrett in Sydney, with Damian McKenzie a prime contender for the bench role following his brilliant effort at five-eighth in the third Test against France six weeks ago.

Mo'unga made his Test debut late in that Dunedin Test.

"Richie couldn't have done anything more than he's done this year for the Crusaders, he's been outstanding," Hansen said.

"Every time I go to [AMI Stadium] I get told to put him in the team, and I walk away thinking 'we've already put him in the team'. He's in the squad, he's 24 years old, he's played one test match, he's got competition from the specialist five-eighth in Beauden Barrett."