To be considered a rookie, a player must have entered a season below each of the following thresholds:
- 130 at-bats or 50 innings pitched in the Major Leagues.
- 45 total days on an active Major League roster prior to Sept. 1, when clubs are allowed to expand their rosters from the 25-player limit to include any player on the 40-man roster.
From Sept. 1 through the end of the regular season, both at-bats and innings pitched count against rookie eligibility but days on a big league roster do not.
A player must have rookie eligibility to be considered for any MLB rookie awards -- such as the American League or National League Rookie of the Year Award -- or appear on any MLB Pipeline prospect lists.