 Signed by the Toronto Maple Leafs in 1962, Seiling played only one game with the Leafs and spent most of his time as a Toronto prospect in the minors.The next year, he represented Canada at the 1964 Winter Olympics, where they finished in fourth place.He was traded to the New York Rangers, where he would remain for the next decade, except for a brief claim by the St. Louis Blues in the 1967 NHL Expansion Draft, after which he was immediately traded back to the Rangers.