Heartwarming moment AFL rookie learned he'd be debuting

The Melbourne Demons have given a unique insight into the moment Paul Roos broke the news to Christian Petracca that he'd be debuting.

The club set up a hidden camera inside Roos' office when he called Petracca in to reveal his selection ahead of Saturday's clash with St Kilda.

The video above makes for heart-warming viewing as the Melbourne mentor first tells the 20-year-old "it's hard to find a spot" for him.

"But we've found one for you," Roos says before reaching out to shake a shocked Petracca's hand.

The youngster has had an injury-plagued start to his career with a knee reconstruction in 2015 and a broken toe over Christmas.

"You've worked your backside off … and now you can tell your 10,000 Twitter followers and brothers and sisters and cousins."