Hollowell played 38 games with the Niagara Rivermen Minor Midget hockey club, where he tallied 8 goals and 19 assists for 27 points.

[7] He returned to the Greyhounds where he ended the 2017–18 season fifth amongst leading scoring OHL defencemen with 12 goals and 44 assists in 63 games.

[9] Prior to the start of his season as an overager, Hollowell was named an alternate captain alongside Jordan Sambrook and Morgan Frost.

[8] At the conclusion of his OHL career, Hollowell joined the Toronto Marlies of the American Hockey League (AHL) during their Calder Cup run.

[12] Upon making the jump to professional hockey, Hollowell remarked "The guys are bigger and older and positionally smarter, so I'm just trying to find ways to play my game.

[18] On October 28, 2020, with the upcoming 2020–21 season delayed by the ongoing pandemic, Hollowell was loaned to Finnish second division club, TUTO Hockey of the Mestis.

[21] He was placed on waivers by the Rangers on October 1, 2023[22] and after going unclaimed, was assigned to New York's AHL affiliate, the Hartford Wolf Pack to start the 2023–24 season.