In 1894, Mack became the manager of the Pittsburgh Pirates of the National League (NL). He tried to draft Bergen, but the contract was voided when the Pirates assigned the catcher to a minor league team, a practice which major league teams were not allowed to do at the time. The minor league team was Lewiston of the New England League, for whom Bergen played even though he was no longer under contract with Pittsburgh. Playing 97 games, Bergen batted .321.
