Career
He is currently playing with the Erie Otters of the Ontario Hockey League (OHL). Dermott was rated as a top prospect who was projected as a possible first round pick in the 2015 National Hockey League Entry Draft. He was ultimately selected 34th overall by the Toronto Maple Leafs.
Following a strong first year performance with the Erie Otters in which he scored 28 points 67 games, Dermott was rewarded when he was named to the 2013-2014 OHL First All-Rookie Team.
The following season, he scored 45 points in 61 games, including a franchise record seven-game assist streak (the longest such stretch by a defenceman). He also led all Erie defencemen in playoff scoring with 17 points.
On July 22, 2015, Dermott was signed to a three-year, entry-level contract by the Maple Leafs.