Selby started his hockey career with the Toronto Marlboros in the OHA where he played five seasons. Selby got his first taste of a championship win in 1963–64, when the Marlboros swept the Edmonton Oil Kings in 4 games to win their fourth Memorial Cup. In 1964–65, Selby was called up by the Toronto Maple Leafs to replace injured forward Ron Ellis in the NHL. He played 3 games with the Leafs, scoring 2 goals. Selby scored his first NHL goal against the New York Rangers' Jacques Plante in his first NHL game. Ellis would return and the Leafs sent Selby back down to the juniors. The following season, Selby had a full-time roster spot with the Leafs. Selby scored a total of 27 points in his rookie season and was awarded the Calder Memorial Trophy, for best rookie of the season. His total of 27 points is the lowest scoring total by a Calder-winning forward since 1937–38. Struggling early on the next season, the Leafs sent Selby down to the minors to play with the Vancouver Canucks in the WHL. He played 15 games before injuring his leg, sidelining him out for the remainder of the year. In 1967, the NHL expanded by introducing 6 new teams. Selby was claimed by the Philadelphia Flyers in the Expansion Draft. During his first year with the Flyers, Selby set career highs in goals, assists, and points. The Flyers traded Selby back to his old team, the Maple Leafs, in 1968–69. Selby spent one season with the Leafs, before being traded again, this time to the St. Louis Blues. His stay with the Blues would be short however, as he was sent down to the minors with the Kansas City Blues. In 1972–73, a newly formed league, the WorldHockey Association was created. Selby was selected in the WHA General Player Draft by the Houston Aeros. Seeing an opportunity to jump out of the minors, Selby took it and signed on with the Aeros. Before even playing a game with the Aeros, he was immediately traded to the Quebec Nordiques. After playing only 7 games with the Nordiques, he was quickly traded to the Philadelphia Blazers, who in turn traded him to the New England Whalers. He spent 63 games with the Whalers, winning the Avco World Trophy, the WHA championship. In 1973–74, he was traded to the Toronto Toros, where he would retire.
