The All Blacks thrashed the Wallabies 38-7 in front of a huge crowd at the Melbourne Cricket Ground for their third win of a perfect start to 2023.
It also ensured they retain the Bledisloe Cup for a 21st consecutive year, making next week's second Wallabies test in Dunedin a dead rubber.
Having humbled each of the southern hemisphere powers in 2023, the All Blacks appear to be peaking at the right time in a World Cup year.
But Foster joked that he hoped New Zealand media could "damp down" their headlines.
"Keep us under the radar a little bit longer," he said.
"We're trying to build something that gets us where we want to be.
"We've made the point earlier that we feel the best way to prepare for the big stage is to prepare for the big stage every week. And that's what we've had to learn.
"We know that we had some growing up to do as a team, coming into this year. And so far we've taken three pretty strong steps forward, which we're pretty proud of.
"But I'm not sure it's quite enough just yet."
Led by stand-in skipper Ardie Savea, Foster's team ran in seven tries and were brilliant on the last line of defence, denying the Wallabies several five-pointers.
Scrumhalf Cam Roigard made his test debut off the bench and kept the All Blacks' machine purring after replacing Aaron Smith in the second half.
"He'd be delighted," said Foster of the Wellington Hurricanes rookie.
"I talked to him afterwards and his eyes were pretty wide open. Playing at the MCG and looking around in a Bled (Bledisloe) game.
"So I thought he did really well and should be proud of that."