Overview of Baseball’s Minor League Organization

Where the players come from

Only 25 of the players on a Major League Baseball team’s 40-man major league reserve list may be active for the major league club, except from September 1 to the end of the regular season, when teams are allowed to expand their game-day rosters to 40 players. The remaining 15 players are generally either on the disabled list or play at some level of the minor leagues (usually at the AAA or AA level). Players on the 40-man Reserve List are eligible for membership in the Major League Baseball Players Association. The minor league players work at the lower end of major league pay scales and are covered by all rules and player agreements of the players association. Minor league players not on the 40-man Reserve List are under contract to their respective parent Major League Baseball clubs but have no union. They generally work for far less pay as they develop their skills and work their way up the ladder toward the major leagues. Many players have signing bonuses and other additional compensation that can run into the millions of dollars, although that is generally reserved for early round draft picks.

Even though minor league players are paid considerably less than their major league counterparts, they are nevertheless paid for their services and are thus considered professional athletes. Baseball cards refer to “pro record” and “pro seasons” as including both major and minor leagues. For this reason, minor league players generally consider it an insult when someone asks when they’re going to “get to the pros”. More accurately, a player’s aim is to reach “The Show” or the “big leagues.”

Current system

Under most circumstances, minor league teams are not owned by Major league clubs, but have affiliation contracts with them. A small number of minor league clubs are directly owned by major league clubs, but these are rare. Major league Rule 56 governs the standard terms of a Player Development Contract (PDC) which is the standard agreement of association between a minor league team and its major league affiliate. Generally, the parent major league club pays the salaries and benefits of uniformed personnel (players and coaches) and bats and balls, while the minor league club pays for in-season travel and other operational expenses.

Minor league teams often change their affiliation with major league clubs for a variety of reasons. Sometimes Major or Minor League Clubs wish to affiliate with a partner that is geographically closer. In recent years, some MLB clubs have attempted to place as many affiliated teams within their Blackout Area, to make scouting and player transfers more convenient and to take advantage of the existing fan base (interest in the parent team builds support for the minor league affiliate and early fan interest in developing minor league players reinforces support for the parent team as “local players” reach the majors). Sometimes a Minor League Club wishes to improve the caliber of players its major league affiliate sends to play there. Sometimes a major league club wishes to improve the facility where it will send its developing players. In even-numbered years, any Major or Minor League club with an expiring
PDC may notify Major League Baseball or Minor League Baseball, respectively, of its desire to explore a re-affiliation with a different PDC partner. The Major League Baseball and Minor League Baseball offices then send a list of the corresponding Major and Minor League Clubs seeking new affiliations, and there is a limited period of time in September within which clubs may agree upon new PDCs. If any are left over after this process, the Major League Baseball and Minor League Baseball offices are empowered to assign Major and Minor League clubs to each other.

Going into the 2010 season, the longest continuous link between major league and minor league clubs was the link between the Orioles and their Rookie-level Appalachian League affiliate, the Bluefield Orioles. The teams were affiliated for 53 years, from 1958 through 2010. Baltimore ended the PDC after the 2010 season. At the start of the 2011 season, the longest continuous affiliation will be the 45-year link between the Philadelphia Phillies and their Double-A Eastern League affiliate, the Reading Phillies. The Reading club is owned by the Philadelphia organization.

The current minor league classification system divides leagues into one of five classes, those being Triple-A (AAA), Double-A (AA), Class A (Single-A or A), Class A Short Season, and Rookie. Furthermore, Class A is further subdivided into Class A Advanced, and Class A. Under the rules governing the affiliated minor leagues (specifically Major League Baseball Rule 51), Class A Short Season is a separate classification from the other leagues bearing the “Class A” name, despite the similarity in name.


This classification currently includes two affiliated leagues: the International League and the Pacific Coast League.[1] Triple-A leagues usually hold many of the remaining 15 players of the 40-man major league roster whom the major league club has chosen not to play at the major league level. It has recently been referred to as a “spare parts” classification, because frequently a player who is good enough for the majors (especially if he had signed with a team needing someone to play his natural position) is held in reserve at the minor league level for major league emergencies. Some veteran minor league players are informally called “Four A” players, meaning they are generally regarded as more experienced than a Triple-A player on his way up, yet are not talented enough to stay in the major leagues or do not project as having as much growth in their abilities as those who are less experienced. Some of the top prospects might be assigned here if they are not quite ready for the major leagues, with the potential to be called up later in the season. This is often called the holding cell for the players ready for the bigs.

Players at this level from the 40-man roster of a major league team can be invited to come up to the major league club once the major league roster expands on September 1, although teams will usually wait until their affiliates’ playoff runs are over, should they qualify. For teams in contention for a pennant, it gives them fresh players. For those not in contention, it gives them an opportunity to evaluate their second-tier players against major-league competition.

In addition to the two affiliated Triple-A leagues, the Mexican League is classed a Triple-A league, though its clubs do not have PDCs with Major League clubs.


There are currently three leagues in this classification: Eastern League, Southern League, and the Texas League. [1] Some players will jump to the majors from this level, as many of the top prospects are put here to play against each other, rather than against minor and major league veterans in Triple-A. A small handful of players might be placed here to start, usually veterans from foreign leagues with more experience in professional baseball. The expectation is usually that these players will be in the majors by the end of the season, as their salaries tend to be higher than those of most prospects.

Unlike the major league and the Triple-A level, two of the three Double-A leagues have their season divided in to two parts, the Eastern League being the exception. One team may clinch a spot in the playoffs by winning the division in first half of the season, then the teams’ records are cleared and another team will also clinch a playoff slot during the second half. Wild cards are used to fill out the remaining teams; usually, four teams qualify for the league playoffs. This system is used at the Class A level as well.

Class A

Class A is a classification comprising two subclassifications: Class A-Advanced and Class A. Players usually have less experience or have particular issues to work out; pitching control and batting consistency are the two most frequent reasons for a player to be assigned to Class A baseball.

Class A-Advanced
One level below Double-A, the California League, Florida State League, and the Carolina League play at the Class A-Advanced level.[1] This is often a second or third promotion for a minor league player, although a few high first-round draftees, particularly those with college experience, will jump to this level. These leagues play a complete season like Triple-A and Double-A, April through early September. Many of these teams, especially in the Florida State League, are owned by major league parent clubs and use their spring training complexes.

Class A
Slightly below Class A-Advanced, are the full season Class-A leagues, South Atlantic League and Midwest League.[1] These leagues are a mix of players moving up from the Short-Season A and Rookie leagues, as well as the occasional experienced first-year player. This is the lowest classification to play a full season.

Class A-Short Season

Class A-Short Season, despite sharing the “Class A” designation with the above leagues, is in fact a separate classification from Class A. Players are assigned to Short Season A teams for more or less the same reasons that apply to Class A; however, Short Season A teams are slightly
more limited than Class A teams with respect to player age and years of experience in professional baseball.

As the name implies, these leagues play a shortened season, starting in June and ending in early September (thus, there are only a few off-days during the season).

Short-season leagues consists of the New York-Penn League and Northwest League and is the highest level short-season affiliate for 22 MLB organizations.[1] The remaining eight clubs have their highest level short-season affiliate in either the Appalachian or Pioneer Leagues, which are officially classified as “Rookie” level leagues.

The late start to the season is designed to allow college players to complete the College World Series, which runs through late-June, before turning professional, give major league teams time to sign their newest draftees, and immediately place them in a competitive league. Players in these leagues are a mixture of newly-signed draftees and second-year pros who weren’t ready to move on, or for whom there was not space at a higher level to move up. Second-year pros tend to be assigned to extended spring training until the short-season leagues begin.

For many players, this is the first time they have ever used wooden baseball bats, because aluminum bats are most common in the amateur game, as well as the first time they have played every day for a prolonged basis, as amateur competitions typically regulate the number of games played in a week. Players are permitted to use certain approved composite bats at this classification, to help them make the transition from aluminum to wood bats.


Leagues in the Rookie classification play a shortened season similar to the Short-Season A classification leagues, starting in June and ending in early September. This lowest level of minor league baseball consists of six leagues, the Appalachian League, Pioneer League, Arizona League, Gulf Coast League, Dominican Summer League, and Venezuelan Summer League.[1] The Appalachian and Pioneer leagues are actually hybrid leagues; while officially classed as “Rookie” leagues, several major league teams have their higher-class short season teams in those leagues. These teams also maintain Rookie-level teams in other leagues as well. All of the other Rookie leagues are short season leagues as well.