He played for the St. Michael's College School Monarchs as a 155-pound, fast-skating left winger, in 1951. He worked out with Toronto for the first time in February 1949, along with Tim Horton. Because of an Ontario Hockey Association rule, the two college players were not allowed to play for the Toronto Marlborosa Maple Leafs affiliatein that junior ice hockey league. Leafs' President Conn Smythe did not like the ruling but granted the junior players a trial after four of his team's forwards were injured. In October 1953 Hannigan sustained a rib injury in practice and was out of the Maple Leafs lineup for three weeks.
