Pietersen returns to the Springbok side for his first international involvement of the season. The Japan-based flyer is part of a hugely experienced backline named by head coach Heyneke Meyer, with Jaque Fourie alongside captain Jean de Villiers in the centre and Morné Steyn and Fourie du Preez at half back.
Walker will savour his first taste of international rugby on Saturday and Pietersen says the Ospreys man can provide a real threat to the South African defence.
"I'm up against Walker and it's his debut game so it's going to be quite a test for me," he said.
"From what I've heard of him he's an exciting winger so it will be an interesting challenge.
"He backs himself to score tries and he's a very exciting finisher."
Pietersen added: "I know exactly how it feels to be a guy making your debut. You want to cement your place at international level and prove you're a good player.
"If you play at this level everyone is world class and as a winger, I need to be on my game 100 per cent and not give him an opportunity."
The Wild Nights back is returning to a South Africa side which impressed in the recent Rugby Championship. First up for Meyer's side this autumn is a clash with Wales before meetings with Scotland and France.
"It's an exciting but very nervous time to be back in the Springbok mix because they had such a good year," said Pietersen.
"It feels like you're a little boy again but it's going to be a big game on Saturday and it's a pleasure to be back.
"I've played twice at the Millennium Stadium before and I think it's one of the best stadiums any rugby player can play in. It's a great experience and a great crowd.
"Wales are on a high after the success with the British & Irish Lions so it will be a difficult encounter for us as Springboks.
"I have to bring my A game on Saturday and give my best for the team. We play every game to win so we are not coming here for a break. It's going to be a great encounter and it won't be easy."