There's been plenty of hype surrounding Aumua, ever since his barnstorming performances at the Under-20 World Championship earlier this year, but Hansen's trying to keep a lid on expectations for the exciting hooker.
"If we're being honest, he's probably overwhelmed by it all. There's a lot that we've got to help him with, and we'll do that nice and slowly.
After more than a year out of the squad, Seta Tamanivalu will start on the left-wing, where he made a big impression in his debut season with the Crusaders.
The 25-year-old has certainly impressed Hansen, after shifting position from centre to the wing.
"He's good aerially, he's a good ball carrier and he seems to be more comfortable there defensively."
Openside flanker Matt Todd wasn't considered, due to his groin injury, meaning Ardie Savea will start in the No 7 jersey, where he'll come up against older brother Julian, who'll likely be on the wing for the Barbarians.
Often billed as a "festival match", Hansen still thinks there'll be plenty of intensity on Sunday morning, with 13 New Zealanders in the opposition squad.
"This will be a tough game, I'm picking. It's like a New Zealand trial, so everyone will have plenty to say about it.
"It'll give us a good gauge of where they're at - 70,000 people expected to be there so a big atmosphere... how they cope with that."