At the age of 15, he was selected in Western Australia's team for the under-16 national championships and was named captain.
Now Duncan's leadership skills are coming to the fore at Geelong.
In March, the 22-year-old, who has played 81 games since making his debut in 2010, was elevated to the Cats' leadership group after receiving the backing of his teammates and coaches.
It was another step forward for a highly talented and motivated young man who is committed to having a positive impact at his club.
"To get in the leadership group, it's obviously great that your peers have noticed those kind of qualities about you," Duncan told geelongcats.com.au.
"But I haven't changed anything. I'm still the same person around the club and still voice my opinion when I think I have to.
"I think I'm just learning a lot more about the footy club at the moment, being in the leadership group. There are lots of different topics to discuss.
"It's mainly for me at the moment about learning different ways to lead and help people."
Duncan has some great elders to learn from, as Geelong's leadership group contains players like Harry Taylor, Steve Johnson and the indomitable Joel Selwood.
"He epitomises a footy player, really. He's quite remarkable," Duncan said of Selwood.
"He's taken a few points off Lingy and Harls (former Geelong skippers Cameron Ling and Tom Harley), but he's a completely different leader to what they were.
"He's being himself and leading his team the right way."
Might Duncan one day captain Geelong?
"Looking down the track, I'll keep going in the leadership group and we'll see how things go from there," he said
Right now, Duncan is doing all he can to ensure the Cats spend another season near the top of the ladder.
He was quiet against Adelaide and the Brisbane Lions in rounds one and two, before returning to form with a 30-possession game against Collingwood in round three.
He backed that up with further good performances in the wins over West Coast in round four and Hawthorn on Easter Monday.
"I thought I had a slow start, but the last few weeks have been more up to the standards that I'm setting," Duncan said. "As long as we're winning, I don't really care too much."
Added Cats coach Chris Scott: "He's had some slightly different roles this year as well, where he's had a little bit of a defensive bias to his role.
"While he's done that role well, it hasn't impacted negatively on his offensive output."
This weekend, Geelong takes on Port Adelaide in a top-of-the-table clash at Adelaide Oval.
The Cats are coming off a six-day break but have had a lighter training load to compensate.
"We definitely won't be using that as an excuse if we happen to lose," Duncan said.
Stopping the Power's run will be a key for Geelong.
But Duncan is confident that the Cats have the fitness to get the job done.
"They're a fit side and (Port coach) Kenny (Hinkley) has them working really hard," he said.
"But we think we had a pretty hard pre-season. It's probably the hardest one I've ever done, which is good. I had no injuries and it's good for myself and for the team.
"We're running out quarters pretty well. In the last quarter on Monday we kicked a few more goals than Hawthorn … so we'll definitely back our fitness in as well."
