Beauden Barrett might not be starting, but he says he's worked harder than ever ahead of a possible test debut after being named in the reserves for the third test against Ireland tomorrow night.

After his first two weeks with the All Blacks, the Taranaki and Hurricanes first five-eighth said he had learnt a lot from watching Dan Carter, and now Aaron Cruden, prepare for a test match.

"The way they've controlled a team from Monday to Friday, not just on the field, it's quite a lot of work behind the scenes that you guys don't see," he said.

"It's not an easy job being a No10 and there's a lot of work to do off the field."

Although there was no guarantee he would get on the field in Hamilton, 21-year-old Barrett was buzzing at the prospect of wearing the black jersey.

"Very excited, yep. It's been a dream for me and a goal for a long time. If I get the opportunity, I'll be rapt and I'll grab it with both hands," he said.

All Blacks coach Steve Hansen said he had every faith in both of his first five-eighths after Carter's withdrawal on Tuesday because of a hamstring strain.

"We have a lot of faith in Aaron Cruden; he came on well in the first test, he's played Super Rugby extremely well and I'm expecting nothing less of him when he pulls on his test jersey

"The young fella's [Barrett] brand new, but he's a pretty confident, cheeky wee man and I'm sure he'll be raring to go."

Cruden said he was relaxed and ready to fill in for Carter.

While the six changes to the All Blacks side – including the absence of Carter and No8 Kieran Read – will give Ireland hope, they will not see Cruden as a weak link.

"When I first came in, I was really nervous," the 23-year-old player said.

"[Then] I changed a lot of my techniques and routines in the way I approached things because I didn't want to not note everything down or miss something and let the team down.

"I think coming in now, I'm a lot more relaxed.

"I'm stuck in my routine that's been working for me for the past couple of years.

"I'm just doing that no matter what team I'm playing for, whether it's Manawatu, the Chiefs, or the All Blacks."

What a contrast to the bloke who made a nervy start against Australia in Sydney in 2010, and was pulled after 61 minutes as the All Blacks scraped home 23-22. It seems a lifetime ago. Cruden stepped up during the 20-6 World Cup semifinal win over the Wallabies. He has not looked back.

His move from the Hurricanes to the Chiefs has taken his game to the point where the shadow of Carter, although still there, is no longer the stuff of nightmares.

Cruden still sees the man he has replaced as the "best in the world", but is comfortable with the task of putting Carter under pressure.

That's a big change from the then 21-year-old who was just glad to get a run when he made his test debut against Ireland two years ago with a breezy 27 minutes during the 66-28 win in New Plymouth.

Significantly, Cruden's fourth start in 10 tests will be the first time he has taken the goal-kicking duties into an international. Notably, he puts his Super Rugby success – he's running at 82 per cent this season – down to less practice.

"In past years, I've been almost goal kicking every day and if it wasn't really working I'd try and change something to help my technique and it seemed to make it worse.

"This year, I've just relaxed about it and I'm set in my technique and it [the ball] seems to be going over the sticks, which is great."

- © Fairfax NZ News