The most anticipated homegrown prospect the Toronto Maple Leafs have had in decades stepped on the ice after a group of seven- and eight-year-olds working on defensive skills finished their morning practice. Mitch Marner had only an hour to skate before the next pack of novice and tyke players would arrive for afternoon lessons at 3 Zones Hockey School in Ajax, Ont. He set up on the goal line and at the instruction of the school’s director, Rob Desveaux, began to pirouette down the ice. “Turn! Turn! Go!” Desveaux shouted, following behind as Marner spun twice on his right skate then switched to his left before spinning twice again. “Turn!”

Marner continued, progressing in 720-degree one-legged spins down the length of the ice and back. A brief bag skate followed the drill, then a series of shooting speed and release exercises, all with Desveaux correcting and challenging as though the CHL Player of the Year were some young kid trying to make a rep team. Marner had just come from an upper-body workout session at the Leafs’ practice facility, where he’d been training all summer. He dripped sweat as he chugged a bottle of water at the bench during a brief break. He let out an exhausted curse, smiled and headed out for the next gruelling drill set up by the grey-haired, 60-year-old Desveaux. “Ah, this just sucks!” he said, skating to centre ice. Marner wore a white practice sweater with the logo of the team that drafted him fourth overall in 2015 on the front, the team he’s dreamed of playing for since he was a boy growing up just north of Toronto. Now on the edge of that dream, he fired a puck on a Shooter-Tutor while wide-eyed kids coming in for the afternoon session packed against the glass to get a look at him. Marner was doing everything he could to finally break into the NHL. But will it be enough?

Doubt has chased Marner throughout his young career in hockey. It’s almost laughable for a kid with his natural scoring ability, but as he fast-tracked through levels in the game, he always ran up against others’ concerns that he was too small and too weak to make it all the way to the pros. Despite being one of the top minor hockey players in Ontario, the undersized forward fell to 19th in the OHL draft in 2013. He became a junior-hockey superstar with the London Knights, leading the powerhouse franchise to the Memorial Cup last May. He scored 44 points in the OHL playoffs alone. Still, Marner’s complete domination of junior hockey hasn’t quashed doubts about his NHL readiness. The Leafs have offered him no assurances that he’ll be on the roster this fall. But as Tor­onto enters a new era on the ice—centred around 2016 first-overall pick Auston Matthews—the locally grown right-winger is confident he can be a key part of the franchise’s suddenly promising future. And if he’s going to get there, it’ll be with the skills that have carried him past every doubt he’s faced before.