As a big league manager with four teams—the Indians (1935–1937), Tigers (1943–1948), Red Sox (1950–51) and Philadelphia Phillies (1952–1954)—O'Neill never had a losing record. His Tigers won the 1945 World Series (when they defeated the Chicago Cubs in the Cubs' last Fall Classic appearance until 2016) and O'Neill was known for turning around under-performing teams, often in mid-season.