Although rated by many AFL scouts as the second best forward in last year's draft class, behind No.1 pick Tom Boyd, McCarthy will make his debut on Sunday in defence against the Western Bulldogs.

The West Australian teenager would be forgiven for having somewhat of an identity crisis given how his playing roles have changed – and it's not just limited to football.

As a kid, McCarthy's first dream was to play AFL though that changed when he entered his teens and he realised he was too small to get a kick.

"That's not getting me anywhere and I got really into cricket," said McCarthy, who now stands an imposing 193cm.

As an opening bowler, his lack of size also proved a problem, depriving him of speed, but he found a way around it. He became an opening batsman.

McCarthy was good enough to make it as far as Western Australia's under 17 squad but his dream of wearing the baggy green evaporated not long after missing out on a tour of Tasmania.

"It was a bit of a bummer for me, then footy season came and I thought I'd give it a red hot crack and here I am now," McCarthy said.

McCarthy's break came when he was spotted by talent scouts for South Fremantle's colts side.

Despite having played primarily at local level as a junior, McCarthy quickly established himself as one of the best key position prospects of his draft year.

But he will face red-hot competition for a forward's berth at the Giants, who have already stockpiled Jeremy Cameron, Jonathon Patton, Adam Tomlinson and Boyd.

Before this year, McCarthy figured he had played just one quarter in defence but has played primarily in that position this year in the NEAFL for the Giants.

"As a forward you're trying to get rid of your man and finding the footy and getting into space," McCarthy said.

"You're looking to get kicked to, and swinging into the backline you're on your man and locking down. That was probably the hardest to get used to, locking on and not worrying about the footy as much."

Although McCarthy still loves cricket, and regularly chats to club runner Simon Katich about the game, he is glad he pursued football.

Had he not, McCarthy said he would most likely be playing grade cricket in Perth.

"I'd be working and slugging away," McCarthy said.

"I've always had a passion for footy, I gave it a real crack and reaped my rewards for it. I couldn't ask for a better job in the world."