Dahlgren was the Red Sox’ first baseman as a rookie in 1935, but was displaced in 1936 when Boston acquired Jimmie Foxx. He dropped to the minors, and in 1937 played third base for the championship Newark (International League) club. On May 2, 1939, he played first base for the Yankees in place of the ailing Lou Gehrig, whose consecutive-game string thus ended at 2,130. Dahlgren homered that day, and he remained the Yankee first baseman for two seasons. He saw regular action, mostly in the NL, through the end of WWII.