But that thrill was quickly tempered when he ran his eyes over a list of his new teammates and wondered how on earth he was going to ever play a senior match.
"I was happy and then thought, gee, I'll have to wait two or three years just to get a game. I just decided to train as hard as I could and that paid off," Duncan told afl.com.au.
"I did everything I could to play AFL footy. I didn't particularly want to play VFL and when I had that taste I didn't want to get dropped."
But Duncan, who is this week's nomination for the NAB AFL Rising Star award, didn't have to wait too long as he was in the Cats' round-one team last year.
He made seven more appearances for the season but was unable to cement his spot in the side.
That looks to be a different case this year as Duncan has barely put a foot wrong in the first three rounds.
Impressive performances against St Kilda and Fremantle were followed up with a 24-disposal, two-goal effort in Sunday's win over Port Adelaide.
It was a display that the NAB AFL Rising Star committee could not ignore.
Duncan says his taste of the big time last year showed him what he had to develop to become a regular senior player
And he worked feverishly on all his perceived weaknesses which he said he wasn't aware of while playing for WAFL side East Perth.
"The defensive side of the game, my decision-making and all my contested ball stuff and just being a bit harder in the contests are the main things I tried to work on over the pre-season," he said.
"Last year it was a lot quicker than WAFL footy. This year I'm getting used to it and getting a hang of the tempo. I think it's starting to show a bit."
Duncan is not the only emerging player forcing his way into the formidable Geelong side, with Taylor Hunt, Daniel Menzel and Allen Christensen all impressing in Sunday's win over Port Adelaide.
"We know we have to step up because some of the senior guys are getting older. We push that as a group that we want to put pressure on the older guys. So it's great to see them getting games as well. Any one of them could have won the rising star this week as well," he said.
"We've all seen Menzel's tricks. He's caught the eye of a couple of people and Taylor Hunt is very consistent and uses the ball well off half-back."
