When Marco Tilio faces former club Sydney FC in his first A-League grand final, it will be the culmination of a calculated risk and a lot of hard work.

The 19-year-old was surrounded by success at Sydney FC, but never really tasted it himself at senior level.

He won the golden boot in a 2019-20 Y-League championship team and was a part of the A-League squad that won last season's premiers plate, but played just three games for a total of 12 minutes plus a goal.

Tilio wasn't in the team that won last year's grand final and less than a month later, headed south to join City on a three-year deal.

The hard work was just beginning

City's fitness regime is a make-or-break one and Tilio got a first-hand experience of the "tough" and "mentally draining" build-up of a Patrick Kisnorbo preseason.

"It started off rough, knowing that I was coming into a club that's all about physical and mental attributes," Tilio told AAP.

"Coming in not as fit as they would like and then just working extremely hard throughout preseason into almost the first half of the season to get to the fitness level to be able to play.

"Once I was able to do that and got an opportunity to play it was just time to take my opportunities, and I think it's come pretty good towards the back end. So I'm proud of that."

But even once he'd proved his fitness there were still no guarantees for the 19-year-old.

City had one of the most well-credentialed attacking trios in the league: Jamie Maclaren, Craig Noone and Andrew Nabbout, meaning Tilio had to bide his time off the bench before breaking through.

Tilio first got a real look-in as a starter when Nabbout went down with an adductor tear, and he made the most of it making 20 regular-season appearances where he started in eight and scored a goal.

"That was the goal coming over to Melbourne - I knew I'd get opportunity and it has come," he said.

"I just wanted to put my best foot forward when I'd get the opportunities to play. Just building confidence and performing were my biggest targets."

Then when Maclaren left for Socceroos duties and Nabbout and Noone (knee) had injury setbacks, all of a sudden the responsibility fell to Tilio and Stefan Colakovski in last week's semi-final. They they didn't shy away from it.

Tilio teed up Colakovski for the opener before scoring himself, with the 2-0 win sealing a home grand final.

"All the odds were against us coming to Sydney and all the rest of it, having our supposed home final against an opposition in their home (city)," Tilio said.

"Just to get out there and play in a semi-final was unbelievable and then what me and Cola were able to produce to help the team, it was an incredible feeling."

Tilio had plenty of family on hand at the semi-final win in Sydney but given the border restrictions and lockdown facing the city, they'll be watching the decider from home.

But the 19-year-old knows he'll have plenty of support on the field at AAMI Park on Sunday, whether his more well-credentialed teammates in Noone and Nabbout feature or not.

Tilio credits "the original front three" of Noone, Nabbout and Maclaren with getting he and Colakovski ready to make their mark on the biggest day of the season, when City will hunt their first A-League championship.

"They've been incredible all year on and off the field," he said.

The younger boys look up to them in training. Throughout everything we've done this year, they've been incredible role models to us, it's just a privilege to learn off them each day."

"The camaraderie with our squad is second-to-none. The group of boys we have - we're so tight.

"From the backroom staff to the players, everyone's one big family and I think nothing can break us as a group.

"We've deserved everything we've got this year (by) working extremely hard. There's only one more game to go and I think we can do it."