In the absence of Richie Mo'unga on paternity leave, and only he and Beauden Barrett in the All Blacks tour group as specialist first five-eighths, McKenzie has been entrusted with the playmaking role against an Argentine side looking to make up for a disappointing loss last week.
McKenzie with 34 Tests - 13 as a substitute and 20 starting at fullback - played his only other starting role at first-five against France, at Dunedin, in 2018. That was a 49-14 victory where McKenzie crossed for two tries and landed seven conversions.
McKenzie said Brisbane this weekend was an opportunity to have a chance in the position. He was comfortable taking it on after starts in Super Rugby, with the Chiefs, and as a substitute in Tests.
"It's a challenge, and I'm looking forward to it," he said.
Preparing for the role was not too different from the approach he took when playing fullback. But he now had the 'keys to the bus', so it was about getting his game management sorted.
Confidence built during the week's preparation for a game, and he had concentrated on nailing that during the build-up.
What was different about starting was the requirement to break the opposition down instead of coming on as a substitute when play tended to open up more, something that suited his natural running type of game.
Beauden Barrett had been working with him during the tour, and learning from him had helped him be confident in what he could do on the field.
"As a driver, I want to be in the game as much as possible, so it's about creating opportunities for other people around me and just making sure I'm in control and driving the team around the park where it needs to be.
"It's different, but that's not to say I'm going to chuck everything I know out the window and go to be a robotic player. I've still got to play my game," he said.
With Chiefs team-mate Quinn Tupaea starting outside him at second five-eighths, McKenzie said they would be looking to play their games and not try to be anyone else.
"Quinn had a great season for us carrying the ball so we'll look to do the simple things well and stick with what we know. If we can do that I'm sure everything else can flow off and we can put some good stuff together," he said.