The Blackhawks repeatedly called up Mitchell and demoted him six times within a span of only 1.5 weeks. When he finally had the chance to play, it was in a forward position, despite being a defenseman.
During the 2020-21 season, Mitchell made his NHL debut and participated in 39 games for the Blackhawks. However, he faced difficulties and spent most of the subsequent season in the AHL. His journey to the NHL was impeded by injuries and obstacles within the organization.