With Hawthorn boasting two New Zealand teens on their books, St Kilda have also decided to delve into the untapped talent pool on this side of the Tasman.
It's easy to understand why, with the same qualities that see players shine in rugby or league - speed, strength and agility - doubling as attributes highly sought after in Australian Rules.
Mountain-Silbery certainly ticks those boxes, excelling in athletics at school and recording a personal best of 11.36s in the 100m. His proficiency in league attracted the attention of the South Sydney Rabbitohs but St Kilda, who play an annual Anzac Day fixture in Wellington, struck first.
"I live in a predominantly league family and they wanted me to use AFL to help with offseason stuff, like kicking," Mountain-Silbery said.
"A close family friend told me to try AFL and that's where I was noticed by the NZ AFL trainers. They told me to come along and give AFL a good crack.
"This whole opportunity is massive and it's something really new. It's a new experience for me and my family and I'm just really excited to take this opportunity as it comes and get the ball rolling."
Mountain-Silbery will remain in Auckland to complete his education, honing his Australian Rules skills through weekly trainings with a local coach.
He's also set to spend the next school holidays visiting the club - his first trip to Melbourne - to further learn the game he has played for only a matter a months.
"I watched a couple of their games last year," he said.
"I just love the whole kicking and jumping, how they were able to get so high on to other players' shoulders - that was really cool.
"And I've been introduced to a few rules, which did take me by surprise because I'm used to all the league rules."
Shane Savage, one of only a handful of New Zealand-born players to feature in the AFL, was confident Mountain-Silbery would be able to make the adjustment to his newly-chosen sport.
The 23-year-old Savage is yet to make his debut for St Kilda, having switched to the Saints following a 57-game stint for Hawthorn, but he was hopeful Mountain-Silbery could follow in his footsteps.
"He's a big boy - it looks like he's ready to go," Savage said.
"I'm really looking forward to seeing him develop over the next couple of years and all the teammates back in Melbourne are really looking forward to meeting him.
"There's great opportunities for New Zealand players to go over to the AFL and have a really big impact," Savage said.
"We know, especially their physiques, they're all ready to go and they've got the attributes to play.
"It's just about teaching them that craft - how to kick and how to handball. If you can accomplish that then they can have a real impact at AFL level."
