Growing up in Sydney meant the Swans were his go-to team, with the champion goalkicker his first sporting idol. Mills joined the local Auskick clinic in North Shore, following his grandfather Ray Mills, who played for Perth and Western Australia in the 1960s.
But his interest in Australian football looked set to be short-lived. At age seven, Mills dropped those ambitions, picked up another oval ball and followed his friends to start playing rugby union.
That stint lasted six years, and he was good at it, making the representative Warringah Rats side as a five-eighth. One year he combined playing Australian football with rugby, which for a long while took precedence.
That was until one of his dad's close friends Andrew Pridham, then on the Swans board and now its chairman, asked Mills to fill-in for his son's team, the Mosman Swans.
"I put my hand up and backed up from rugby, and I really enjoyed it actually, it was good fun," the 17-year-old told AFL.com.au.
"I like rugby, but I don't. There's multiple things that I hate about the game. It's not really fun, it's really one-dimensional, it's just a line.
"They run into you, you tackle, they run into you, you tackle. With AFL it's much better, it's all around the ground and I get to use my endurance, which I really like."
The Swans then asked Mills, as a 13-year-old, to be part of the club's academy, which presented a few new experiences for the tough, composed and classy midfielder.
"The coach called us in and everyone started high-fiving each other saying 'Well done', and I'd never seen that before. It was pretty foreign for me. I didn't know what was going on, but I really enjoyed it. As soon as I was in that program I loved it and I stopped union straight away," he said.
It is hard to imagine the Swans could have foreseen how much they might benefit from Pridham's offer down the track.
Mills is not eligible for the NAB AFL Draft until 2015, but has already got people talking.
As a bottom-aged prospect this season, Mills came into the NSW/ACT Rams under-18 team wanting to cement his spot, and show he's "not a little kid who doesn't know what he's doing".
He's done more than that, averaging 30 disposals in five games at TAC Cup level. He took that form into the NAB AFL Under-18 Championships, too, averaging 21 disposals over three rounds and being named in the All Australian side.
Some recruiters say he is the best player of next year's crop, able to dig into packs, cleanly gather and feed the ball out, and have no hesitation doing it over and over.
At 185cm, Mills is brave in the air, runs and runs, distributes precisely and enjoys the physical stuff. There is an intensity to his play – when Mills is around the ball, you expect him to end up with it and then do the right thing with it.
But like one of this year's draft's best midfielders, Isaac Heeney, Mills is already linked to the Swans under the academy system. They will get first access to him.
"The Swans academy has been great for me. There's still a lot of water to go under the bridge so I'm just making sure I play good footy every week. I want to do it, for sure. But it's still a long way away and I haven't really thought about it yet," Mills said.
As some have noted, Mills is ahead of where Heeney was this time last year. The competitiveness between them might be a reason for that.
"At training we go head-to-head and he really challenges me. He helps me set the standards at training and I follow him. I see things he does and I try to better them," he said.
"We were doing a one-on-one drill at Rams training on a Thursday night and we had a TAC Cup game a couple of days after, and we were going full on. And he smacked me one up near the jaw, and the ball was coming in so we were wrestling, then I got him down, and he pulled me down.
"It was just a battle. We don't like losing to each other. We're good mates off the field, but when it's on the field we turn against each other."
