That shift allows Sam Cane to come on to the bench with a prospective debut for the 20-year-old.
Thomson has started 15 times in his 25 tests since his debut against Ireland five years ago in Wellington.
He has been in superb form this year for the Highlanders, used out wide on attack and defence and being his usual reliable source of lineout ball. Pace and stamina allow Thomson to roam all across the park, where his skills at the breakdown and in support create regular scoring chances.
That style suits the Highlanders and Super 15 rugby but may not be the template Hansen and his coaching staff want from the All Black blindside flanker.
Jerome Kaino became a brutal defender for the test side, a lineout option and a bruising blindside flanker who dominated the close channels but could also sortie a shade wider.
His injury absence this season left the selectors with the choice among Vito, Thomson and standby flanker Liam Messam.
Vito's volume and standard of Super 15 work for the Hurricanes and his leadership persuaded the selectors he was the best replacement for Kaino.
However, an untimely knee ligament injury at Eden Park has put his career on hold for about five weeks.
Thomson's promotion will provoke guesswork about whether he will be asked to modify his style to suit the All Black plans or be encouraged to continue with the methods which have been so productive at Super 15 level.
His style could add another dimension to the All Black backplay, which already looked threatening in the opening test against Ireland.
Or it may prompt the All Blacks to use a left and right flanker approach which they have tried before with mixed success.
Thomson has started 11 of his tests on the blindside, splitting the rest of his games between openside, No 8 and coming from the bench.
Coach Hansen said this week had been about preparing well again and building on the foundations from the 42-10 first test victory.
"We are expecting further improvements in our game due to the extra training and preparation time we have had together, along with having a game under our belt," he said.
"We are also expecting Ireland to improve, as they are a nation with a 'never-say-die' attitude so what we did last time won't be good enough."
Hansen said the All Blacks and test rugby's return to a new 21,000 sold-out venue in Christchurch would be a great boost to the earthquake-hit city.
"The team, especially those of us from Christchurch, know that people have still been doing it tough, so, hopefully, we can give them a performance on Saturday that puts a smile on their faces."
All Blacks
1. Tony Woodcock (84)
2. Andrew Hore (63)
3. Owen Franks (32)
4. Brodie Retallick (1)
5. Samuel Whitelock (26)
6. Adam Thomson (25)
7. Richie McCaw - captain (104)
8. Kieran Read (37)
9. Aaron Smith (1)
10. Daniel Carter (86)
11. Julian Savea (1)
12. Sonny Bill Williams (15)
13. Conrad Smith (56)
14. Zac Guildford (9)
15. Israel Dagg (13)
Reserves:
16. Hikawera Elliot (3)
17. Ben Franks (16)
18. Ali Williams (74)
19. Sam Cane *
20. Piri Weepu (57)
21. Aaron Cruden (10)
22. Ben Smith (3)