In his playing days (1932–52), he was a first baseman and veteran minor-leaguer who appeared in two full MLB seasons during the World War II manpower shortage, with the 1943 Boston Braves and the 1945 Chicago White Sox, batting .262 with 177 hits, no home runs and 55 runs batted in in 188 games played.

He also pitched in five games for the 1943 Braves, losing his only decision and compiling an earned run average of 4.30 in 23 innings of work.

At the close of the 1956 season, after his club had won 88 games and finished as runners-up to the New York Yankees, Cleveland Indians manager Al López resigned to become the new skipper of the White Sox and Farrell was promoted to succeed him.

Prodigal left-handed pitcher Herb Score, a strikeout king and 20-game winner in 1956, was nearly blinded on May 7 by a line drive off the bat of the Yankees' Gil McDougald, and missed the rest of the campaign.

The Indians fell to a 76–77 (.497) record and a sixth-place finish, the team changed general managers (from Hank Greenberg to Frank Lane), and Farrell was fired.