The world champions are without six regular second rowers, leading to Pieter-Steph du Toit moving from flank to lock, and Ruan Nortje earning only a third international cap for the Test at Ellis Park.
"The depth and experience and talent of South African rugby ... whoever they put out there, they are in a Test jersey and will do their country proud, we know that," Hansen told reporters.
"They're the rugby world champions and they're playing like it. They're confident in their game and their brand of forward power, kicking pressure, and also their ability to use the ball.
"What you have to understand is the depth and excitement of South African rugby. It's unbelievable."
South Africa have a full haul of 10 points from their first two Rugby Championship fixtures in Australia, while New Zealand are second in the table with five and need to win at least one of their two games in South Africa to stay in contention.
"It's a hell of an opportunity and challenge for us on Saturday. We know how good they are," Hansen said. "They have the ability to go through you, around you, over you, so we have to be right on with our game, we'll have to be at our best.
"It's been really exciting to hear the stories around what it's like to be out there at Ellis Park. I know the rivalry. I've watched it from afar and I've respected it."
New Zealand coach Scott Robertson will name his team on Thursday for the game at high altitude in Johannesburg.
