Gagnon, 26, was originally drafted by the Calgary Stampeders in the sixth-round (52nd overall) of the 2017 CFL draft. The Quebec native attended training camp with Calgary this season before being released prior to the start of the regular season. Gagnon also played in two preseason games for the Stamps in 2017, recording one defensive tackle and two special teams tackles, before returning to the University of Sherbrooke for his final season of eligibility.
Over five seasons (2013-17) with Sherbrooke, Gagnon played 36 regular-season contests and totalled 80 tackles including 23.5 tackles for loss, 13 sacks, nine pass breakups, two forced fumbles and one fumble recovery. In 2017, he led the Vert et Or with 4.5 sacks and also had 24.5 tackles including 7.5 tackles for loss and two pass breakups.