Kammala jumla mai zuwa: Walman ya buga wasan hockey na matasa tare da Toronto Jr. Canadiens a cikin Ontario Junior Hockey League (OJHL) kafin ya shiga wasan hockey na kwaleji tare da Providence College na Hockey East. Kafin lokacinsa na farko tare da Friars, an zaɓi Walman a
2014 NHL Entry Draft a zagaye na uku, 82nd gaba ɗaya, ta St. Louis Blues.