He played professionally from 1960 to 1982, including his first 15 seasons with the Toronto Maple Leafs where he won the Calder Memorial Trophy and four Stanley Cup Championships, and was inducted into the Hockey Hall of Fame in 1986.

[1] On October 16, 2016, as part of the Toronto Maple Leafs centennial celebrations, Keon was named the greatest player in the team's history.

In his second year in the NHL, Keon was named to the second All-Star team and won the Lady Byng Memorial Trophy as the most gentlemanly player, taking only one minor penalty through the entire season.

In the 1967 Cup Final, he shut down Jean Béliveau, the star centreman of the Montreal Canadiens, in the last two games of the series and was voted the most valuable player of the playoffs, winning the Conn Smythe Trophy.

Keon's eight points are the fewest ever by a non-goalie Conn Smythe winner, and he remains the only Leaf to have won the trophy named for the former owner of the club.

Keon signed a letter of intent with the Nationals and received a $50,000 cheque from the team, but the deal fell apart just before training camp.

The Leafs believed they had some strong young prospects at centre who needed more ice time, and Keon was again asking for a contract with a no-trade clause.

The 35-year-old Keon was told he could make his own deal with another NHL team, but any club signing him would have been required to provide compensation to the Leafs.

[10] In August 1975, with the Leafs still controlling his NHL rights, Keon reluctantly jumped to the World Hockey Association, signing a deal with the Minnesota Fighting Saints reportedly worth $300,000 over two seasons.

The New York Islanders expressed a strong interest in signing Keon, but they needed to negotiate a deal for his NHL rights with the Leafs.

Again, the Leafs' asking price (said to have been a first-round draft pick) was too high, and a disappointed Keon signed with the WHA's Indianapolis Racers in March 1976.

Keon's WHA rights were briefly claimed by the Edmonton Oilers, but they immediately agreed to trade him to the New England Whalers.

[10] Other Leaf players who clashed with Ballard's management did reconcile, most notably Keon's successor as club captain, Darryl Sittler, who accepted an invitation from GM Cliff Fletcher to return as a consultant after the team came under the ownership of Steve Stavro.

[12] In 2005, he told the Toronto Sun that the new owners (majority equity owned by the Ontario Teachers' Pension Plan, chaired by Larry Tanenbaum) "would like to say they are different, but they are all the same.

"[13] In January 2007, the Toronto Maple Leafs announced that Keon would attend a pre-game ceremony to honour its 1967 Stanley Cup-winning team.

[16] On January 21, 2016, it was announced that Keon, along with former Maple Leafs Turk Broda and Tim Horton, would be commemorated with a statue on Legends Row in front of the Air Canada Centre, joining former Maple Leafs greats Syl Apps, Teeder Kennedy, Johnny Bower, George Armstrong, Darryl Sittler, Borje Salming, and Mats Sundin.