"We'd like him to get the opportunity to come through the starting process and bring his game to the party and use Piri to come off the bench and if we need to change the game we can do that or if we need his experience at the end of the game we can use that."
The 23-year-old Smith said he wouldn't hesitate to order the more experienced forwards around if necessary.
"That will be something I have to come to terms with but hopefully there's mutual respect there and they knowing I'm saying what needs to be said for the good for the team," he said.
Hansen had no doubts either.
"He's a cheeky wee man and the forwards love him. The forwards just expect halfbacks to talk. Coaches do too and halfbacks are obliging because they like talking."
Chiefs lock Retallick deserved his chance in front of Ali Williams, Hansen said. And Hurricanes wing Savea was another player in excellent form.
When asked about Retallick's ability to cope with the physical demands of test rugby, Hansen said: "He's coped with it at the level below. We're making the assumption that he can. I've got every confidence and so have the other coaches."
Victor Vito has got the nod at blindside flanker, replacing the injured Jerome Kaino who set new standards in physicality in this position. Hansen said picking Vito ahead of Adam Thomson that he was backing the Hurricane to mature into a Kaino-like figure.
"Adam Thomson has had a big season with the Highlanders and we're really looking to Victor to bring his physical game, to be honest. Thommo can concentrate this week on catching his breath and coming off the bench."
Asked whether Vito could transform into an angry player given his pleasant personality, Hansen replied: "Jerome Kaino's a nice bloke too. Brad Thorn's not a bad bloke either. It's just a maturing thing with Victor. He's been by nature a ball runner but as his game has matured he's got better and better in that area."
Sonny Bill Williams has predictably been selected at second-five ahead of Ma'a Nonu, with Hansen impressed by the strides the Chiefs midfielder and league convert has made.
"Brad Thorn took about four years to go from a converted player to understanding the game and we're seeing exactly the same thing happening with Sonny. Three or four years where he has come to our game with a number of skills but he didn't know when to unlock them or when to use them. This season we're seeing a guy who is actually understanding the game and the role that he has in it. We know he's a freak and he can do whatever he wants with the ball. Having that understanding is making him go up three or four levels."
All Blacks team to play Ireland at Eden Park on Saturday: (test caps in brackets)
1. Tony Woodcock (83)
2. Andrew Hore (62)
3. Owen Franks (31)
4. Brodie Retallick *
5. Samuel Whitelock (25)
6. Victor Vito (13)
7. Richie McCaw (c) (103)
8. Kieran Read (36)
9. Aaron Smith *
10. Daniel Carter (85)
11. Julian Savea *
12. Sonny Bill Williams (14)
13. Conrad Smith (55)
14. Zac Guildford (8)
15. Israel Dagg (12)
* Debut
Reserves:
16. Hikawera Elliot (2)
17. Ben Franks (15)
18. Ali Williams (73)
19. Adam Thomson (24)
20. Piri Weepu (56)
21. Aaron Cruden (9)
22. Ben Smith (2)