 Born in Penetanguishene, Ontario, Marchildon pitched 1,214 innings with a won-lost record of 68 wins and 75 losses and a career ERA of 3.93 for the Philadelphia Athletics and the Boston Red Sox from 1940 to 1942 and from 1945 to 1950.All but one of his 185 MLB games pitched came in an A's uniform.Marchildon had two standout seasons for Philadelphia, going 17–14 for the 1942 Athletics and 19–9 (3.22) for the 1947 edition.