GREATER Western Sydney will unveil prized No.3 pick Finn Callaghan for footy's toughest test against Melbourne at the MCG on Saturday night.

The 18-year-old wingman was told of his debut by co-captain and mentor Josh Kelly, following two dominant weeks in the VFL.

The Melburnian will run out for his first AFL game in his home city in front of an expected group of 30 friends and family and on to the MCG for the first time since playing Auskick at half-time of a Hawthorn-Collingwood clash 10 years ago.

"It's been my dream for a very long time since I started playing footy, it's really exciting and a proud moment for me and my family," he said.

"When it got announced yesterday, I was just full of excitement and I already want to get out there and play."

While Callaghan was a Bulldogs supporter growing up, his father Brett - who ran for Australia in the 400m at the Commonwealth Games - has been a passionate Demons fan up until his son's recruitment to GWS.

It adds another element of excitement around the talented teen's AFL debut.

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"It's all worked out so well, playing the ‘G, lucky enough to have all my friends and family there, playing in Melbourne, it'll be so good," he said.

"Mum and Dad were both really excited, Mum showed a bit more emotion and was very proud, Dad was a bit more measured in his response as most dads are and he's just very happy.

"He's fully on the Giants bandwagon now, he's converted over from the Dees which is great.

"It's exciting for them as well as they've helped me out a lot along the way."

Callaghan admits his debut has come a little earlier than expected having only returned to full fitness in the past month following a foot injury over the pre-season.

But he's been watching on with envy and inspired by fellow early draftees Nick Daicos, Jason Horne-Francis and Josh Rachele, as they adapted so swiftly to the big time.

"I have watched them, it's great to see other boys in your draft year do really well and it's given me confidence that I'll be able to hopefully play as well as they are," he said.

"Obviously it's going to be really tough but if these boys are doing it, why can't I? That's sort of my attitude going into it.

"I'm not 100 per cent sure where I'll play yet, but I hope to bring lots of run and speed and a bit of endurance. I just hope to play on instincts and take the game on when I get the ball and use my kicking to hit up the forwards."

The hype and expectations around No.3 picks are usually heightened and it's been that way for Callaghan over the past 12 months leading into his draft.

Now that he's fully embedded in the AFL system, he's taken notice of what's required to get to the top.   

"The people that work the hardest at the footy club – the Josh Kellys, Toby Greenes, it's that work ethic that does get rewarded," he said.

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"Something I've noticed is that the people who put in the most work, they're the ones playing to the best of their ability."

And he'll get another indication of that against Christian Petracca, Clayton Oliver and co. when he faces up against the best team in the land in his first game on Saturday night.

"It will be a great test but I wouldn't want it any other way first up to play against the best and see what the benchmark is and the level I've got to get to, to match those players," he said.