For Harris it's the culmination of a quick rise through the ranks. A member of the 2012 New Zealand under-20 team, he made his debut for the Chiefs this year, playing 11 matches for his franchise.
If Sunday's test goes to plan for the All Blacks, Harris might find himself in the action reasonably early in the second half as the coaches seek to save Mealamu's legs for what is likely to be a torrid battle against the Boks at Ellis Park.
Harris will be given time to develop and Coles' example will be of comfort to the coaches.
The now 27-year-old quickly overtook Mealamu this year as first-choice hooker after Andrew Hore's retirement in December.
Renowned for his running and ball skills, Coles has become an extremely accurate lineout thrower and his added bulk allows him to make a greater impact around the field and at scrum time. His high work-rate suits the All Blacks' up-tempo game; he has quickly become an extremely important part of the All Blacks machine.
Hansen said he wouldn't call up another hooker as back-up following Coles' return to New Zealand, although he did have one in mind should another injury strike. Either Highlander Liam Coltman or Chief Rhys Marshall are likely to be next on the list.