Donald Robert "Duffy" Dyer (born August 15, 1945) is an American former professional baseball player who is the manager of the Kenosha Kingfish of the Northwoods League collegiate summer baseball league. He played in Major League Baseball as a catcher for the New York Mets (1968–1974), Pittsburgh Pirates (1975–1978), Montreal Expos (1979), and Detroit Tigers (1980–1981).