The All Blacks were worthy 33-16 winners against an error-strewn Springboks side in the first test in Johannesburg, but Rennie does not expect the four-times world champions to be as poor again.
New Zealand defeated South Africa comfortably in Auckland last year, but the following weekend suffered their worst ever test defeat, a 43-10 humbling in Wellington under former coach Scott Robertson.
"We are aware of the potential bounce-back," Rennie told reporters on Thursday. "They will be bitterly disappointed with last weekend. There has been a lot of talk around how they bounced back last year and we have touched on it (as a team).
"We have also talked a lot about us being better than we were last weekend. Both teams can be a lot better. I would take a one-point win."
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As for where the All Blacks can improve, Rennie believes handling the physicality of the Springboks will be key.
"In the contact areas they were full of energy and we struggled to get forward," he said. "It has been a focus. They are big men and sometimes you just need to carry hard, win races and support well.
"Discipline-wise we gave away soft penalties early in the game. We gave them easy entries into our 22. Scrum-wise we had a couple of issues but we think our scrum will be a lot better."
Rennie is not expecting much of a departure from last week in terms of the Springboks’ gameplan.
"They will just try and do what they did last week but do it better and maybe put more balls in the air, get mauls going and spend as much time as they can in our 22.
"Our energy and scramble held them up over the line a couple of times. They had plenty of time in our 22 but our energy kept them out."
New Zealand climbed to the top of the world rankings with victory last weekend but could lose that spot on Saturday. Not that Rennie is bothered.
"I am not remotely interested in the world rankings. I don’t understand them, they seem to change on a whim. Our focus is only on the game on Saturday," he said.
Rennie named his team for the Cape Town clash earlier on Thursday, making three changes to the starting XV.