While the world champions have been on the end of criticism for their style of play, Plumtree, with his playing and coaching experience in South Africa, knows what they are capable of when the mood takes them.
"I saw them play some pretty good footy in the World Cup and against the [British & Irish] Lions. They can play – they have some outstanding backs. You just don't know what's going to happen on the day, so we've got to be prepared for everything," he said.
Plumtree knows the blowtorch will be applied by South Africa and the All Blacks needed to be ready to deal with it.
"When it comes to these two teams, the form book gets thrown out the window.
"There's so much respect for each other's games, what's happened the last couple of weeks really doesn't matter," he said.
The All Blacks had been improving with each outing while South Africa would have been disappointed in their play in Australia.
"I've seen a lot of these contests, and they're often pretty close in the final quarter. We're expected a titanic battle up front, and there are some obvious parts of their game we have to worry about as well," he said.
Given their lack of results there would be plenty of emphasis on defence by the South Africans who have used line speed as one of their cornerstones.
"There's only really one way to stop line speed, and that's if we put them on the back foot, and that's where the forwards come into play. Our set piece, how we carry the ball, our cleanout work – we can't let the Boks get set and come off the line hard," he said.
And being the 100th Test between the sides some elements never change, especially the forward contest.
"Up front is where it's going to be won and lost," Plumtree said.
"This will be the toughest forward battle since I've been involved.
"Everything we do has to have more power and speed. We've got to play at a high tempo because that's our game. We can't fall into the trap of the game slowing down.
"They'll be hurting a lot. They're a very proud rugby nation. They'll have a bit of a corral mentality, especially around their own media and fans. When they start getting stuck into the Springboks, they become a more dangerous animal.
"It's too late for them to change the way they want to play – that just wouldn't make sense. But they'll be looking at areas that are letting them down and have given them success. Their kicking game is a real weapon.
"The coaching team will be smart enough to not over-react to the last couple of weeks, they'll be looking at parts of their game they've got to get better at, and also at parts of our game that are obvious threats.
"I've watched these games over the years, and to be involved in one is a bit of a dream come true for me. I get a lot of messages from South Africa and New Zealand when we do well, so I'm caught in the middle of it all, but there's only one team I want to win in the weekend," he said.