Holl, 27, has established new career-highs for games played (38), assists (10) and points (1-10-11) with the Maple Leafs in 2019-20. In 51 career NHL games, he has registered three goals and 11 assists for 14 points. He became the first Maple Leaf and sixth NHL defenceman in history to record a goal in his first two NHL games in 2017-18. Holl also appeared in 192 career AHL regular season games with the Toronto Marlies, recording 68 points (20 goals, 48 assists). He added 16 points (4 goals, 12 assists) in 46 career Calder Cup playoff games, capturing the Calder Cup as a member of the Marlies in 2018. He represented Toronto at the 2018 AHL All-Star Classic.
Holl originally joined the Maple Leafs organization on July 23, 2015 after signing an AHL contract with the Toronto Marlies. He signed his first contract with the Maple Leafs on July 2, 2016.