Saturday's Test at Eden Park will be the 26-year-old's first start against South Africa and bring him head-to-head with a hulking Springbok pack and arguably the best hooker in the world, Bismarck du Plessis.
"A little bit nervous but I can't wait to get out there ... and have a crack against a very good physical side," Coles said in Auckland.
"Growing up watching the All Blacks the big one was always against South Africa and one you always dream about playing against.
"I'm really overwhelmed to get the opportunity to run out against one of the best sides in the world (and it) is going to be awesome."
The decision to give Coles, who has started just two of his eight previous Tests, the number two jersey is an invitation to prove himself in the white hot atmosphere of a match against one of his country's greatest rivals.
"He is somebody we see as the future and now is the time to give him an opportunity to go against the best, so we are comfortable with where he's at," Hansen said.
"Nothing is make or break, he is the guy we see going forward and it does not mean he will start next week or be in the group for the next Test.
"But we think it is time to give him an opportunity in the big ball park and see how he goes."
The vote of confidence in Coles is also indicative of Hansen's long-term planning for the 2015 World Cup as Andrew Hore and Keven Mealamu approach the twilight of their careers.
Hore has denied reports he will retire after the Rugby Championship but turns 35 on Friday, while 34-year-old Mealamu has been blighted by leg injuries over the last two seasons.
While it is doubtful whether either will be around by 2015, Hansen has used them in a mentoring role with Coles and brought a promising young hooker into the squad each week to experience the Test environment.
"That's why we held on to the two oldies, but 2015 I do not see Horey being there and I don't think he sees himself being there," said Hansen.
"At some point we have to make a change and we need Colesy to be ready when we make a change."