Barclay Graham Plager (March 26, 1941 – February 6, 1988) was a Canadian professional ice hockey defenceman and coach for the St. Louis Blues.
His reputation was established while still in juniors, when he had a notable fight with his own brother Bob, who was playing for the rival Guelph Royals.
With the 1967 NHL Expansion, many new jobs opened up in the National Hockey League, and Plager was acquired with Red Berenson by the St. Louis Blues from the New York Rangers, which held his rights.
He retired as a player during the following season when he was named as head coach of the Blues, succeeding Leo Boivin.
In 1984, he was diagnosed with inoperable brain tumors and had to undergo chemotherapy treatments after suffering dizzy spells thought to be the result of an old head injury.