"It's almost natural for me to play with a chip on my shoulder, (considering) where I came from," Mangiapane said Tuesday. "I've always been doubted.
"So, every time I step onto that ice, I try to work my hardest."
Mangiapane wasn't drafted into the OHL, but willed his way onto the Barrie Colts roster as a walk-on in 2013. He set the league ablaze, firing back-to-back, 100-plus-point campaigns, and looked to be the next big thing to sprout from the Dale Hawerchuk-led outfit.
But at the time, not even that was enough to earn the praise of the scouting world.
The Flames, though, are thankful for that - scooping the now-23-year-old up in the sixth round, 166th overall, in the deep, 2015 Draft.
A full year after he was eligible.
Now he's getting top-six minutes and is a fixture in the team's offensive attack.
"I always looked up to Martin St. Louis," Mangiapane said. "He was a smaller guy, so I figured if he was a smaller guy playing in the NHL, why can't I? He was my inspiration, a guy I looked up to.
"If you don't get drafted, it's not the end of the world."
Turns out, it was really just the beginning.
Mangiapane arrives at the quarter mark this year on a 31-point pace over 82 games.
But that number is quickly on the rise.
He's always had the hands, but in this - his first full year at hockey's top level - he's beginning to round out and tap into the boundless offensive potential he's always had.
Mangiapane has three points (1G, 2A) in his last five games, applying his craft the only way he knows how. The 5-foot-10, 184-lb. winger is relentless on the forecheck, battling wildly out of his weight class with a dogged pursuit of the puck carrier, leaning on defenders to win back possession, or deliver an unsuspectingly hard hit to help grind the opposition down over time.
Considering his past, none of this comes as a surprise to the head coach.
Snarl and sandpaper have always been a part of his game.