He was immediately assigned to Ottawa's American Hockey League (AHL) affiliate, the Belleville Senators for the remainder of the season.

[3] The following 2021–22 season was over shortly after it began, as Crookshank suffered a season-ending anterior cruciate ligament injury in training camp.

He returned to Belleville for the 2022–23 season and scored a team-leading 26 goals and 47 points in 71 games, good for fourth overall on the team.

[10] On March 1, Crookshank was named the AHL Player of the Month for February after tallying eight goals and 14 points in 12 games.

[11] He finished with 24 goals and 46 points in 50 games with Belleville, before being recalled on March 21 in case Claude Giroux felt he could not play due to an illness.