De Klerk said rival halfback Smith had been a factor in the All Blacks' performances through the years and would be a key player on Sunday [NZT].
"We've become friends off the field, but once we're on the field, it's back to business," he said.
"He's one of their key players with over 100 Tests which makes him unbelievably successful.
"There's a lot to learn from him – it's always good to learn from one of the best players in the world."
South Africa had noted how Ireland overcame the All Blacks in their July series, but they had their way of containing them.
"The important thing is that we need to man-up physically against them, and I don't think we have guys who'll shy away from the physicality.
"We'll work on it with our own plans, and we're not going to try to do something that's not in our embedded DNA," he said.
It was a challenge the Springboks appreciated.
"Playing against New Zealand for South Africa, there's nothing more that you need when you run onto that field, whatever the situation may be. You know it's probably going to be your biggest game of the year, and you're going to have to pitch up."
De Klerk had had a period of dominance in the halfback position with the Springboks but is under more pressure for his place as Jaden Hendrikse has emerged. But de Klerk relishes the challenge that involves.
"There's always been pressure from the other scrum-halves. There are five guys in the camp now, and any of them can be picked on the day.
"I don't think we have similar playing styles and games, but we can do the job that's needed. If you slip once, you may get another chance, but if you slip again, you are gone because the next guy is ready.
"We've got the same thing in other positions, so it doesn't matter if you're experienced, you must pitch up," he said.
"I quite enjoy big games and pressure. I think that's where most of our guys play really well. So it's good to have that feeling so you know you need to perform."