How many games played in a previous season exclude a player from eligibility for Rookie of the Year?

Originally, baseball writers were told to use their own guidelines in determining rookie status. In 1950, Cleveland youngster Al Rosen did not get a single vote, despite his league-leading 37 homers. Boston’s Walt Dropo, who was certainly deserving, won the award instead. However, the determination that Rosen was ineligible based on his 58 previous at-bats, while Dropo’s 41 at-bats were acceptable, did raise some eyebrows. So, in 1957, official specifications were handed down by the league. A player was only a rookie if he had less than 75 at-bats or 45 innings pitched to his credit. He was also disqualified if he had been on a major-league roster between May 15 and September 1. These rules were slightly altered soon after, and the commissioner’s office handed down its final ruling in 1971. Those guidelines state that a player must have less than 130 at-bats, 50 innings pitched, and 45 days on the roster to be eligible for the Rookie of the Year.