McKinnon, a central defender (who had been a winger in his youth during early spells at Junior level),[1][4] made his Rangers debut against Hearts on 8 March 1961 in a 3–0 win at Ibrox. He went on to make 487 appearances for the club in all competitions between 1961 and 1971,[2] winning two Scottish League championships, four Scottish Cups and three League Cups.[5][1]
His final Rangers appearance was in the 1971–72 European Cup Winners' Cup second round match against Sporting CP in Lisbon, where he suffered a broken leg.[5] Rangers went on to win the Cup Winners' Cup that season but McKinnon, who had been a regular for a decade but was already in the latter stages of his career, was put out of action entirely for a year due to the complications of the injury and the poor manner in which it was treated.[4][1]