In the 2016–17 season, Lazar's development with the Senators stalled as his produced 1 assist in 33 games including a demotion to the American Hockey League (AHL) with the Binghamton Senators. On March 1, 2017, Lazar was dealt at the NHL trade deadline by the Senators along with Michael Kostka to the Calgary Flames in exchange for a 2017 second-round pick and Jyrki Jokipakka.