 After two games with the Panthers MacDonald was re-assigned to AHL affiliate, the Springfield Thunderbirds, for the remainder of the season.MacDonald assumed a top-pairing role with the Thunderbirds and in 72 games he led all blueliners in scoring with 14 goals and 43 points.Following his first season in Florida, on June 29, 2019, MacDonald was traded by the Panthers to the Colorado Avalanche in exchange for Dominic Toninato.