On 16 June 2012, Armia was signed to a three-year entry level contract with the Buffalo Sabres. During his second North American professional season in 2014–15, Armia was recalled from Buffalo's American Hockey League (AHL) affiliate, the Rochester Americans, and made his NHL debut with the Sabres against the Detroit Red Wings on 23 December 2014. He was then returned to the Americans before being traded on February 11, 2015, the Sabres sent Armia, alongside Tyler Myers, Drew Stafford, Brendan Lemieux and a conditional first-round draft pick in 2015 (Jack Roslovic), to the Winnipeg Jets in exchange for Evander Kane, Zach Bogosian and the rights to goaltender Jason Kasdorf.