After attending the Kings' 2016 training camp, Černák was re-assigned to their American Hockey League (AHL) affiliate, the Ontario Reign, training camp. Despite an impressive play at the AHL level, he was returned to junior to play a second season with the Ontario Hockey League (OHL)'s Erie Otters for the 2016–17 season. On 26 February 2017, the Kings traded Černák (along with Peter Budaj and a 2017 seventh-round draft pick) to the Tampa Bay Lightning in exchange for goaltender Ben Bishop and a 2017 fifth-round pick.