Rickey, creator of the modern and extensive farm system during the 1920s and 1930s, played a critical role in inventing the need for a general manager as well: with most teams coming to own or affiliate with multiple minor league teams from Class D to the top tier, and with dozens (and in some cases hundreds) of players under contract, they needed a front-office infrastructure to oversee the major league club, scouting and player procurement, minor league operations and player development, and business affairs.