The All Blacks' mental state was not something that should concern the Springboks, he said.
"We can only live in our reality, because that is all we can control.
"It is useless for us to spend energy thinking about how the All Blacks are feeling and what they could change – we have no control over that, and the moment you start spending energy on that stuff, you are wasting it," he said.
"We can only control what we can control, and we must make sure they are not more desperate on the day – that we can control."
South Africa couldn't control how the All Blacks approached the game and what they did to contain the Springboks maul and style of play.
"We must stay in reality – that we can control. And as for desperation…these two teams are always in that state when they play each other.
"It goes with the territory. It is automatic, because both sides value these games as extremely special."
Nienaber has made three changes to his side that finished the Test series against Wales.
Kurt-Lee Arendse has replaced injured wing Cheslin Kolbe. Arendse made his mark during South Africa's second Test loss to Wales in Bloemfontein.
"We feel we are replacing like with like, because he has many similarities to Cheslin.
"They come from the same Sevens background, and thus are both devastating on attack and tenacious in defence," he said.
Faf de Klerk returns at halfback ahead of Jaden Hendrikse and that was down to his big game experience.
"We have won some very big games with Faf in the past, be it a World Cup or the British & Irish Lions. He is the man for the inevitable high-pressure situations in this game. We need him and his skill-set for this particular game."
Malcolm Marx will start in recognition of it being his 50th Test match.
"When a player reaches a milestone, we like to make it special for them if it is possible, and it fits the team dynamic.
"Malcolm is a true warrior, and he epitomises what we stand for as the Springboks," Nienaber said.