The Philadelphia Flyers planned to have Hart spend 2018-19, his first pro season, with Lehigh Valley of the American Hockey League after being named the Western Hockey League Player of the Year and Canadian Hockey League Goaltender of the Year in 2017-18. But injuries and inconsistency forced them to bring him up in mid-December, after 18 AHL games, and he wasted no time showing why the Flyers took him in the second round (No. 48) of the 2016 NHL Draft.
Hart won his NHL debut Dec. 18, 2018 against the Detroit Red Wings, then defeated the Nashville Predators two nights later. He became the first goalie in Flyers history to win four straight starts before turning 21 during a streak of eight consecutive victories from Jan. 14-Feb. 9, 2019.