Now let's check out a player who got sent back to the minors through the quirk of an old baseball rule. Harmon Killebrew played 22 seasons of baseball for the Washington Senators (later the Minnesota Twins) and the Kansas City Royals. He was a power hitter, known for both his number of home runs and his home-run distance. When he retired, he was second only to Babe Ruth for the most home runs in the American League and he had the most home runs hit by a right-hander. In his best season, 1969, Killebrew was chosen as the American League's MVP. An accomplished player, he also has the distinction of being a "bonus baby."
Killebrew signed a contract with the Senators in 1954, which included a hefty signing bonus. The Bonus Rule (which ended in 1965 when major league baseball created the draft) stated that if you gave a player a signing bonus of more than $4,000, he had to stay on your 40-man roster for two full seasons before he could be sent down to the minors. If you violated the rule, then another team could claim the player. MLB instituted this rule to keep teams with the most money from luring the best players with big bonuses and then "storing" them in the minor leagues. So players who signed under this rule often went straight to the majors, and those who were signed under the strictest version of the rule were known as "bonus babies." Killebrew is the only bonus baby who went on to become a Hall of Famer that spent time in the minors at all. His playing was uneven, and he was sent down to the minors at the end of his second season. Killebrew struggled for the next two years as well, moving up and down within the farm-team system and playing just 22 games for the Senators. He became a major leaguer for good in 1959, which was his breakout season.