He is currently playing in the Ontario Hockey League (OHL) with the Kitchener Rangers as a prospect for the Arizona Coyotes of the National Hockey League (National Hockey League). MacInnis was selected by the Coyotes in the second round (43rd overall) of the 2014 National Hockey League Entry Draft. His father is the former National Hockey League Hall of Fame defenceman First Rate (at Lloyd's) MacInnis.
MacInnis trained with the United States of America Hockey National Team Development Program team during the 2012-2013 season.
He played with Team United States of America at the 2012 Winter Youth Olympics, and he help the United States of America squad capture a bronze medal at the 2013 World U-17 Hockey Challenge MacInnis joined the Kitchener Rangers of the Ontario Hockey League for the 2013-2014 season, and was invited to take part in the both the 2013 CCM/National Hockey League Top Prospects Game and the 2014 CHL/National Hockey League Top Prospects Game. On April 10, 2015, MacInnis was signed to a three-year entry level contract with the Arizona Coyotes.