"We've spoken about what areas we believe he can continue to improve ... and he was receptive to going back and addressing those things. In the end, it wasn't an easy decision because he is undoubtedly a world-class player."
The move has seen White thrust into the starting side, and the 23-year-old revealed Genia had been giving him more than just wise words in the countdown to his first test starting role.
"He's not only offered advice, he's also given me two pairs of boots," White said.
"He gets given a lot of pairs and had a couple left over.
"Most of the guys up here have size 13, 14 boots. So it's pretty rare to have two blokes with size 10."
White was told of his promotion before training on Monday.
The 1.73m speedster was a five-eighth during his early schooldays, and grew up idolising Stephen Larkham - now his Brumbies backline coach.
But after making the switch to halfback when he was 15, he took a greater interest in another Wallabies and Brumbies great, George Gregan.
White made his test debut only last month, but has impressed McKenzie during his three appearances off the bench.
He was on the verge of making his test debut last year, only for a shoulder reconstruction to rule him out of action.
Australia: James Slipper, Stephen Moore, Ben Alexander, Rob Simmons, Kane Douglas, Scott Fardy, Michael Hooper, Ben Mowen (captain), Nic White, Quade Cooper, Nick Cummins, Christian Leali'ifano, Adam Ashley-Cooper, James O'Connor, Israel Folau. Reserves: Saia Fainga'a, Scott Sio, Sekope Kepu, Sitaleki Timani, Ben McCalman, Will Genia, Matt Toomua, Tevita Kuridrani.
Argentina: Juan Martin Hernandez, Horacio Agulla, Gonzalo Tiesi, Felipe Contepomi, Juan Imhoff, Nicolas Sanchez, Tomas Cubelli, Juan Manuel Leguizamon, Pablo Matera, Juan Martin Fernandez Lobbe, Julio Farias Cabello, Manuel Carizza, Juan Figallo, Agustin Creevy, Marcos Ayerza. Reserves: Eusebio Guinazu, Nahuel Lobo, Juan Pablo Orlandi, Mariano Galarza, Benjamin Macome, Martin Landajo, Santiago Fernandez, Lucas Gonzalez Amorosino.
- AAP