Although born in Hamilton, Ontario, Blair MacKasey moved with his family to Montreal while he was a child. He planted himself firmly in the Montreal sporting scene, playing Junior A hockey with the Montreal Junior Canadiens as well as baseball in the Montreal Expos system. In fact, Blair played one season of ball in Jamestown New York followed by another at Cocoa Beach Florida, attempting to reach the Major Leagues with his hometown Expos. But it was at hockey that MacKasey made his mark.
Drafted by Washington in 1975, he attended the Capitals camp before being sent to Richmond of the American Hockey League. Prior the 1976-77 season, he was traded to the Toronto Maple Leafs, getting into his only NHL game with the Leafs during that season and recording a minor penalty.
MacKasey spent the rest of the season with the Leafs AHL affiliate in Dallas. But while in Texas, the big defenseman hurt his back. The pain increased as the season progressed, and eventually moved into his right leg and forced Blair to prematurely conclude his season. X-rays showed one of his lower vertebrae was out of place, and the ensuing surgery ended Blair MacKasey's hockey career.