"I've played more games at 13 than 12 but I back myself to do the job if needed," he said. "So it's going to be a good challenge but hopefully Conrad and Ma'a are all good and we'll see what happens from there.
"If I do have to slide in there I'm going to have either Ma'a or Conrad beside me so those guys have played a lot of test-match rugby and they'll be able to help me through it."
Despite playing at fullback during the June tests against England, Smith said he was at home on the wing too.
"I've played a bit of rugby now at wing so I'm pretty comfortable there and I'm just looking forward to the opportunity of getting out there and starting another test match."
Smith's versatility also extends to the sevens domain where he has played at first-receiver for the national side, which indicates he should have the ball skills to play at second-five this weekend, if required.
While left wing Julian Savea has been scoring tries at will for the All Blacks - 26 five-pointers in 25 tests - those wearing the No 14 jersey have been less prolific this year.
Smith didn't read too much in to it though and said there were other ways to making a meaningful contribution than scoring tries.
"It's just finding ways to get in to the game," the 28-year-old said. "So I think as we all know, different parts of the game go in different directions and it's just trying to make sure that you're involved in some way."
South Africa have made only one change to the side that lost 24-23 to Australia in Perth last Saturday with the more attacking-minded Handre Pollard installed at first-five instead of Morne Steyn.
"They're two different players," Smith said. "And I think Pollard's shown that he enjoys running the ball and to go with that he has got a good kicking game."
That kicking game could keep Smith busy at the Cake Tin on Saturday night if the Springboks choose to back their chase and try and turn the All Blacks around via Pollard's boot.
"They have moved the ball quite well at times too," Smith said. "So I think the conditions on Saturday night will probably determine how both teams play."
Who knows where Smith will pop up though.