Rule 51 – Classification of Minor Leagues

League Classifications

Each minor league shall be classified as AAA, AA, A, Short-Season A, or Rookie League. Leagues in Class A shall be sub-classified as A-Advanced and A-Full (or Intermediate). Leagues in the Rookie class shall be sub-classified as Rookie, Rookie-Advanced, and Rookie-International. The classifications shall be determined by the Commissioner with consultation from the league presidents.


  • Age limits – a player’s age shall be deemed to be the player’s age on June 5 each season
    • Class A-Advanced, Intermediate – no age limits
    • Short-Season A – no more than 4 payers who are 23+
    • Rookie-Advanced – No more than 12 players who are 21+, no more tan 2 players 23+
    • Rookie – No more than 12 players 20+; no more than 4 players 21+. Club may exempt up to 4 additional players who were not drafted in the most recent draft. Club may also exempt up to 4 players in a domestic league if the player is under a visa, has not played domestically in a prior season, and was not eligible for the most recent draft.
  • Service Time limits – A year of minor league service time is accrued in any season a player spends more than 30 days on MLB or MiLB roster, unless the entire year was spent on the DL.
    • Class A-Advanced – no more than 2 players with 6+ years of service
    • Class A-Intermediate – no more than 2 players with 5+ years of service
    • Short-Season A – no more than 3 players with 4+ years service
    • Rookie-Advanced – no player may have 3+ years service
    • Rookie - no player may have 2+ years of service, except players under 20 years old may have 2+ years of service
    • Rookie-International – no player may have 3+ years service
    • A player may gain an additional year at Short-Season A or Rookie Ball if the player changes positions from pitcher to non-pitcher or vice-versa.
  • Roster requirements – All teams at Short-Season A level or below must carry at least ten pitchers as of July 1