Smith's misdemeanour will have to remain the subject of speculation as Hansen said it would be wrong to assume the indiscretion involved alcohol or curfews. Also open to speculation is whether this change at halfback would have been made anyway.
It has been a huge season for Smith and his whirlwind ride from relative obscurity to starting All Black No 9 hit its first major bump last week in Wellington when conditions and a disorderly performance from the pack conspired against him.
Weepu's control and composure were noticeable in the final 20 minutes and there was a sense that he may have done enough to merit a start anyway.
With the guarantee of a dry ball and a fast track under the roof at Forsyth Barr Stadium, the pressure will be on to finally deliver a more fluent and clinical performance. The theme of recent weeks has been missed opportunity and the pairing of Weepu and Aaron Cruden at first-five will be charged with ensuring the team plays rugby in all the right areas of the field.
And if they do that, Hansen wants to see better decision-making all round. To his mind the lack of tries to date is not a backline problem as such.
"The backline has actually scored more set-piece tries than probably any other team playing rugby at the moment,'' said Hansen. "I don't think that is where the issue is - the issue is around our phase play, our broken play. We just haven't made some good decisions. We have created 19 linebreaks, so we are doing that part of the game well. We are just not finishing it off.''
The other changes in the side were driven by a combination of factors. Andrew Hore needed to share some of Keven Mealamu's workload at hooker which is why the former starts. Sam Whitelock had responded well in his cameo last week to the messages the coaches had given him, Liam Messam was the form blindside and Tamati Ellsion provided better cover at second five than Ben Smith - something that was deemed appropriate without Daniel Carter in the mix.
All Blacks team to play South Africa at Forsyth Barr Stadium in Dunedin on Saturday (7.35pm): Israel Dagg, Cory Jane, Conrad Smith, Ma'a Nonu, Julian Savea, Aaron Cruden, Piri Weepu, Kieran Read, Richie McCaw (c), Liam Messam, Sam Whitelock, Luke Romano, Owen Franks, Andrew Hore, Tony Woodcock. Reserves: Keven Mealamu, Charlie Faumuina, Brodie Retallick, Victor Vito, Aaron Smith, Beauden Barrett, Tamati Ellison.