La Plata - Rookie hooker Nathan Harris is expected to make his Test debut for the All Blacks when they face Argentina in the fifth round of the Rugby Championship in La Plata on Saturday after being named on the replacements' bench on Thursday.
Harris, who was expected to make his debut next week against South Africa, was drafted in early due to Dane Coles' trip home to New Zealand to attend the birth of his first child.
Coles had been expected to still be with the team until after the Pumas' clash and then return home, though his partner Sarah went into labour early and he returned to New Zealand. Veteran hooker Keven Mealamu will start.
"We've known that we were going to have to bring Nathan in for the next leg so we're just going one game earlier," Hansen told New Zealand media in Argentina.
"It's not too big of an adjustment at all really.
"We've been training for it; you expected the unexpected. Nathan and Keven have been doing everything. We've planned for it and it's happened.
"I'm looking forward to it actually. It's taken a long time to get him to this point. If he gets through the next two games I'm sure he's going to be a great All Black because they will be the biggest tests he'll ever have."
Cole's rushed return home was the second disruption to Hansen's preparations ahead of the Pumas' clash with Aaron Cruden dropped before the team left for Argentina after he was late arriving for the plane following a night out drinking.
Beauden Barrett, whose previous only start at flyhalf was against Argentina in Napier earlier this month, will replace Cruden in the pivotal role.
Rookie centre Malakai Fekitoa will also start at the unfamiliar inside centre position after Ma'a Nonu was ruled out for the season with a broken arm he sustained against South Africa on September 13.
"Though it's disappointing having Ma'a injured, it is a great opportunity for the young man and one I'm sure he will take," Hansen added of Fekitoa's third test start.
Hansen also brought loose forward Jerome Kaino back into the starting side after the bruising blindside flanker recovered from a hyper-extended elbow that he sustained last month against Australia.
Lock Sam Whitelock also replaces Jeremy Thrush in the second row after he recovered from a rib cartilage injury that he sustained when he fell awkwardly during a lineout against the Pumas at McLean Park.
15 Israel Dagg, 14 Ben Smith, 13 Conrad Smith, 12 Malakai Fekitoa, 11 Julian Savea, 10 Beauden Barrett, 9 Aaron Smith, 8 Kieran Read, 7 Richie McCaw (captain), 6 Jerome Kaino, 5 Sam Whitelock, 4 Brodie Retallick, 3 Owen Franks, 2 Keven Mealamu, 1 Wyatt Crockett
Substitutes: 16 Nathan Harris, 17 Joe Moody, 18 Ben Franks, 19 Jeremy Thrush, 20 Sam Cane, 21 TJ Perenara, 22 Colin Slade, 23 Cory Jane