I wouldn't attribute that much of Lavoie's success to simply dominating with size at the junior level. He's obviously got that size and it's a real asset, but it's not like he's some bully power forward out there just constantly bowling over children and planting himself immovably in scoring areas like "man child" Gadjovich. I see his game as more like Jeff Carter, who is also big, but doesn't regularly use it to bully and dominate physically. Lavoie will lean on guys at times, but most of his success is more about skating in and out of scoring areas with his wicked release, and using the frame and reach to protect the puck. Where even in the NHL, like Carter, Lavoie is still going to be one of the bigger players with a reach advantage and frame to hold guys off the puck.
I'd be pumped with Lavoie in the 2nd too.
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I don't think it's at all realistic though. I'd be absolutely floored if a 6'3" sniper who can skate, coming off a near goal-per-game deep playoff drive, fell out of the first round. Heck, i'd be surprised if he's not gone somewhere in the Top-20.
The league has become massively more accepting of smaller players, drafting them higher without hesitation. But that doesn't mean big guys who can skate and score like Lavoie aren't still highly coveted. Especially considering the "copycat" nature of the league, with everyone coming off of watching some bigger, heavier players finding success later into these NHL Playoffs. And the recency bias of Lavoie showing what he's really capable in his own playoffs.