MELBOURNE young gun Christian Petracca will finally make his much-anticipated debut on Saturday against St Kilda, the club that overlooked him with the No.1 pick in the 2014 NAB AFL Draft. 

Dees coach Paul Roos delivered the good news to Petracca on Wednesday, after holding back the midfield bull despite weeks of sensational VFL form.

"I never thought the day would come to be honest," Petracca told the club's website.

"He (Roos) didn’t really tell me I was playing. He told me there was no spot for me in the team and we were playing good footy, which is true to be honest.

"Then he told me that I was playing and I can't really describe it to be honest – it's all a bit of a blur."

Match preview: Melbourne v St Kilda

Petracca, who was an emergency for the Demons' 33-point win against Richmond on Sunday night, had 26 disposals (17 in the first half) against Williamstown at Casey Fields last weekend to further press his claims for a senior game.

He was long mooted to be the first pick in the 2014 draft before the Saints opted for key forward Paddy McCartin.

Melbourne forced Petracca to break his way into the side, the plan always set out for him to play a month of football at VFL level before being considered for senior selection.

If you count the lead-in VFL practice matches, the 20-year-old reached that requirement and had shown that he was a class above that level.

The fact Petracca is coming back from a season-ending knee injury that wiped away his first season at AFL level in 2015 was also factored into Melbourne's level of caution.

Petracca suffered a small crack to the little toe on his right foot while playing basketball during the Christmas break which delayed his pre-season by a few weeks, and he did not feature in the NAB Challenge.

Fans can expect Petracca to start his career across half-forward, before he eventually has stints in the midfield once he builds his tank.

Petracca is an exciting proposition.

At 186cm and 95kg he is difficult to budge in one-on-one contests, but he also has the power and speed to burst away from packs.

His enthusiasm is infectious – his teammates love his positive attitude – and he excels when given the opportunity to take the game on.

Petracca won't shy away from the big moment – he will embrace it.