Originally drafted by the Pittsburgh in the first round (22nd overall) in the 2014 NHL draft, Kapanen made his NHL debut with the Toronto Maple Leafs one year later in the 2015-16 season. It took nearly three years before he became an NHL regular. In that season, 2018-19, he broke out and made a name for himself in the NHL, setting career highs in goals, assists, and points that stand to this day.