Minor League Baseball, a crucial part of the larger baseball ecosystem, consists of multiple levels of play that are the training grounds for future Major League Baseball stars.
Across the United States and Canada, a total of 120 teams are affiliated with the 30 MLB franchises, providing opportunities for many baseball players to hone their skills and climb the professional ladder.
The structure of Minor League Baseball is organized into four full-season levels, offering various degrees of competitiveness, with hundreds of players filling the rosters of these clubs. Each MLB affiliate has one team per level of full-season play, along with a team in the complex league (Gulf Coast and Arizona).
In 2021, roster limits for all four full-season levels were expanded, allowing teams to accommodate additional players.
This increase aligns with the intention of nurturing the growth and competitiveness of up-and-coming baseball players, as they navigate through the complex and challenging landscape of professional baseball.
In this vast environment, talented players from diverse origins and backgrounds have the chance to showcase their abilities while gaining valuable experience. Minor League Baseball is an integral component of the sport, as it provides a competitive atmosphere for aspiring athletes. The leagues ultimately serve as a launching pad for players who dream of reaching the peak of their sport and becoming successful Major League Baseball players.
Contents
Minor League Baseball Roster Limits
| Level | Roster Limits |
| Triple A | 28 Active Players |
| Double A | 28 Active Players |
| High A and Low A | 30 Active Players |
| Short Season and Rookie Ball | 25 Active Players |
Affiliated Teams
Triple-A (AAA) teams are the highest level of the Minor League system, just below the Major Leagues. They typically feature players who have the potential to play in the MLB shortly, as well as established players who are working on specific skills before returning to the Major League clubs.
Double-A (AA) is the next tier below Triple-A, and it is considered by many as the league where prospects start to blossom. Players at this level possess strong foundational skills and are working toward refining their abilities for promotion to higher levels.
High-A (A+) teams are the third tier of the Minor League system. At this level, players are often younger and less experienced but possess raw talent and potential. Here, they develop their technique and learn vital skills needed for progression in their careers.
Single-A (A) comprises the lowest level of the affiliated Minor League system. Players in Single-A are usually recent draft picks or players signing their first professional contracts.
They will gain valuable experience and develop their skills to progress through the system and potentially reach the Major League level one day.
The professional development of these Minor League players takes place within this four-tier structure. MLB franchises may also maintain one or two complex-based rookie teams in the Arizona Complex League or Florida Complex League and international summer baseball teams in the Dominican Summer League.
Team classifications in the affiliated Minor Leagues:
- Triple-A: 30 teams total
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- International League: 20 teams
- Pacific Coast League: 10 teams
- Double-A: 30 teams total
- Eastern League: 12 teams
- Southern League: 10 teams
- Texas League: 8 teams
- High-A: 30 teams total
- Midwest League: 16 teams
- Northwest League: 14 teams
In addition to the affiliated teams, Minor League Baseball also includes partner leagues, such as the American Association, Frontier League, and Pioneer League.
While these leagues are not directly affiliated with MLB clubs, they provide additional opportunities for players to develop their skills and gain experience in professional baseball.
Major and Minor League Team Relationships
Major League Baseball (MLB) teams maintain relationships with their affiliated Minor League Baseball (MiLB) teams to develop players, known as “farm teams”.
These Minor League teams consist of players who are under the control of a Major League team, either through contracts from free agency or selections from the draft.
This player development allows Major League teams to nurture and keep an eye on prospective talent for their active rosters.
There are currently 120 Minor League clubs in the Professional Development League (PDL), with each of the 30 MLB franchises assigning four teams per franchise. The Minor League teams play across 19 different leagues, such as the American Association, International Association, National League, Western League, Central League, and Atlantic League.
The leagues are further divided into five categories, with Triple-A being the most prestigious of these. Each Minor League category is as follows:
- Triple-A
- Double-A
- High Single-A
- Low Single-A
- Complex League (Gulf Coast and Arizona)
A team’s active roster consists of players eligible to compete in games, while the reserve roster comprises players on the injured list, restricted or suspended list, or who are temporarily inactive. It is essential to mention that Major League players on rehabilitation assignments do not count against active roster limits.
The relationship between Major and Minor League teams allows the MLB franchises to develop raw talent, identify high-potential players, and offer an opportunity for players to gain experience and improve their skills before joining the Major League. This system ensures a steady flow of talent and prepares future MLB stars for their big-league debuts.
Minor League Levels and Leagues
Minor League Baseball (MiLB) comprises various levels and leagues to accommodate a wide range of player development stages. This section will discuss the main levels, including Triple-A, Double-A, High-A, Low-A, Rookie, and Short-Season Leagues, with an emphasis on the new structure rolled out for the 2021 season.
Triple-A
Triple-A is the highest level in minor league baseball, with two leagues operating under this level: the International League and the Pacific Coast League. Talent in these leagues is close to Major League caliber, and players often end up being called up to their affiliated MLB clubs. Each MLB team has one Triple-A affiliate, making a total of 30 Triple-A teams in existence.
Double-A
Just below Triple-A is Double-A, which consists of three leagues: the Eastern League, the Southern League, and the Texas League. Double-A often features prospects with a strong chance of making it to the MLB. Similar to Triple-A, there are 30 Double-A teams, with one affiliate for each MLB franchise.
High-A
The High-A level is one step below Double-A and consists of two leagues: the Midwest League and the Northwest League. These leagues showcase prospects who have shown solid performance at the lower levels and are progressing towards Double-A and beyond. Each MLB team has one High-A affiliate, making a total of 30 High-A teams in operation.
Low-A
Low-A is another critical level for player development, with many young prospects gaining their first exposure to professional baseball. Like the other levels, each MLB team has one Low-A affiliate, for a total of 30 teams. The leagues in this level are typically organized geographically to facilitate travel and regional exposure for young prospects.
Rookie
Rookie leagues are where players begin their careers after being drafted or signed as international free agents. These leagues include the Arizona Complex League, the Florida Complex League, and the Dominican Summer League. Rookie league teams are often affiliated with MLB franchises and serve as the initial steppingstone for future development.
Short-Season Leagues
Short-Season leagues were part of the previous MiLB structure and included leagues like the New York-Penn League and the Northwest League. As of the 2021 season, this level has been discontinued, with most teams moving to full-season leagues like High-A or Low-A.
Minor League Rosters and Players
Active Roster Restrictions
In Minor League Baseball, a team’s active roster is made up of players eligible to compete in games.
This includes position players and pitchers. Rosters typically have a set limit of players, which varies across different levels of play.
For example, in 2021, roster limits for Double-A and Triple-A levels were expanded to accommodate more players.
While the active roster consists of eligible players, a team’s reserve roster comprises players on the injured list, those who are restricted or suspended, or who are temporarily inactive. These players are not allowed to participate in games until their status changes.
Rehabilitation Assignments
Major League Baseball (MLB) players who are recovering from injuries might be assigned to a Minor League team for rehabilitation assignments.
During this time, the MLB players participate in Minor League games to regain their skills and physical condition before returning to their MLB team. Notably, these players on rehabilitation assignments do not count against the active roster limits for the Minor League team they are assigned to.
Having MLB players on rehab assignments offers a unique opportunity for Minor League players to interact with and learn from experienced professionals. The presence of these rookie players also provides valuable exposure and insights for the Minor League teams, coaches, and fans.
Overall, the roster structure within Minor League Baseball ensures that teams have the flexibility to manage their players efficiently while addressing factors such as injuries, restrictions, and rehabilitation assignments.
Recent Changes and the 2021 Season
The 2021 season of Minor League Baseball saw significant restructuring, with a new integrated player development system across 179 teams within 17 leagues spanning 43 states and four provinces. Including the Arizona League (AZL) and the Gulf Coast League (GCL), the entirety now comprises 209 teams across 19 leagues in 44 states and four provinces1.
Some operational changes were introduced in 2021, such as expanded roster limits for full-season levels which had previously been limited to 25 players. Several rule changes were also tested during the season, including limitations on defensive shifts, pickoff attempts, the implementation of bigger bases, and experimentations with “robot umpires.
This transformative season brought new teams, parks, and brands to the forefront of the Minor League, marking a pivotal point in the league’s history4. These changes and adaptations in 2021 have had a direct impact on the players, game strategies, and overall landscape of Minor League Baseball in the United States.