Retallick assumed the captaincy role when Savea left the field last week, and he was chosen ahead of fellow vice-captain Beauden Barrett because the selectors felt Barrett had a lot on his plate in the first five-eighths role driving the side.
Coach Ian Foster said: "It's a chance for Brodie to have a different little task. He's clearly a quality rugby player and I think he responds to a little bit of extra responsibility. I was impressed with how those two worked, particularly in that second half [against Australia last weekend] and some of the tactical moves and conversations were spot on," he said.
Foster said he wasn't surprised at the haste at which Retallick had returned to form at Test level after his Japan stint.
"I think it's taken a little longer than what people think. When he came back in June, we saw in the July series a Brodie Retallick that was…I think I gave him a six out of 10 in the first week, and he went to an eight out of 10 by the end of that series.
"He's a very quick learner. He's much closer now to what he used to be in terms of strength and size, and yet we haven't seen any loss in his aerobic capacity. His aerobic work last week was phenomenal, it was some of the highest numbers we've seen."
Retallick's running metres were very high from a locking perspective, but also his usual efforts.
And while that was the case of Retallick, Foster said his locking partner Scott Barrett also had high numbers in what he felt was one of his best games for the side. Their combined work rate was powerful for the side.
"It was a very high running metre game. Not a lot has been made out of the Wallabies' performance but they test you in terms of the game. You've got to keep pace with them, they play fast and we probably have to play faster," he said.
"He's back, he's confident, he's got the smile on his face, and that's part of the biggest thing with Brodie. When he's settled and he loves the environment, then he can go out and express himself.
"And I don't want a lot to change with that captaincy band. It's one of the challenges of giving it to someone like Brodie, do you force him into someone that he's not? But I'm really comfortable. He knows his role, he's clear and the boys certainly want to follow him," he said.
Having been involved in his first selection for the All Blacks, Foster said he had known what Retallick was capable of for a long time. But he was also aware of the disappointments he went through with injuries between 2017-19.
"He never seemed to be able to come back to the levels he knew on a consistent basis. So I was fully supportive of him having a break, and we've seen the benefit of that in his case. He's fresh, his body's strong, and his mind has always been strong.
"When you get that combination right then he's quite a force, so it's great to have him back," he said.