After attending the Maple Leafs training camp, Gauthier was assigned to the Toronto Marlies for the 2016–17 season.[29] After playing 16 games with the Marlies, Gauthier was recalled to the NHL on December 16, to replace an injured Martin Marincin.[30] Gauthier would eventually record his first career NHL goal on December 22, 2016, against the Colorado Avalanche.[31] Gauthier was subsequently recalled periodically throughout the season but played with the Marlies during their 2017 Calder Cup playoffs run.