But it wasn't until this week in camp in Newcastle that Wallaroos coach Dwayne Nestor fully discovered the layers to her prodigious talent.

The 19-year-old will make a much-anticipated Test debut at outside centre against Japan at No.2 Sportsground on Saturday.

The youngest of four rookies in the run-on side, Lefau-Fakaosilea lived in Auckland until she was 15 and and only became eligible to represent Australia in May.

Nestor wasted little time, fending off any possibility of the Black Ferns stealing the excitement machine.

"I enjoyed giving her the news that she had been selected, knowing she had waited and been very patient," Nestor said.

Rugby is in Lefau-Fakaosilea DNA. She is the niece of Wallabies giant Will Skelton and former All Black Mils Muliaina. Her mother, Tauva, represented Auckland.

"For a girl who is 19 years old, her game sense and knowledge about what she can and can't do, especially around the tackle zone is incredible. Her ability to turn the ball over; it is like having David Pocock in your midfield. Things like that she has continued to show us in camp.

"Obviously she is an outstanding athlete as well."

Lefau-Fakaosilea has another first-timer beside her in midfield in Ariana Hira-Herangi.

"We didn't take any notice if they were debutants or not, we just picked the best players for the game," Nestor said. "We have quality in our squad now. We are having some very hard selection conversations, but they are the conversations I want. If there are some new faces pushing for spots that is great position for us to be in."

Saturday's Test is the first of two against Japan, with the second at North Sydney Oval next Friday.

In a rarity, the teams squared off in a trial, played over three 20-minute periods, on Tuesday.

The Wallaroos pack, whose locks Michaela Leonard and Alisha Hewett stand 20cm taller and weigh nearly 20 kg more their opponents, dominated the set piece.

But Nestor saw enough quality from the Cherry Blossoms, especially at the breakdown and on the counter attack to be wary.

"It was a bit of an unusual thing, playing a trial against a team you are going to play a Test match against," the coach said. "They are very disciplined in their policies around support play and their defensive work. We have to be careful that we don't get loose and they take advantage of that. We have some fast feet on the edge and we will use them when we can at stages. We have to earn the right to go wide first."

Japan have not played a Test since the 2017 World Cup where they lost 29-15 to the Wallaroos in the group stage.

"This will be our first match since the 2017 World Cup, playing against an international side, so we are very excited to play again and have been preparing well," Saki Minami said.

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