Duncan was signed by the Chicago Bears after going undrafted in the 2016 NFL draft. On August 28, 2016, Duncan was waived by the Bears.[2] Duncan participated in the Winnipeg Blue Bombers 2017 training camp, but did not make the final roster.[3][4] Duncan was signed by the BC Lions on February 22, 2018.[5] He was released before the start of the regular season on May 1, 2018.[6] He signed with the Ottawa Redblacks on May 20, and released on June 10.[6]