The 2021 Minor League Restructuring
How Major League Baseball cut its affiliated minor-league system from 160 clubs to 120 in 2021, what changed in the levels, the draft and the schedule, and what happened to the teams that lost their affiliations.
Before the 2021 season, Major League Baseball had about 160 affiliated minor-league clubs. Afterward it had 120. That single change, made in the aftermath of a cancelled 2020 season, rewrote the map of professional baseball in the United States: roughly 40 communities that had been part of the farm system for decades or generations were no longer part of it, and every major-league organization ended up with exactly four full-season affiliates.
The restructuring was not a minor housekeeping step. It reordered the classification levels, eliminated the short-season leagues, ended the traditional relationship between the major leagues and the governing body of the minors, and was accompanied by a shorter draft, new facility standards and a new weekly schedule. Supporters called it overdue modernization. Critics called it a contraction that cost small towns their teams. Both descriptions are partly right.
This article explains what the system looked like before, what changed in 2021, what happened to the clubs that were left out and what the new structure means for prospects and fans. The details are described as they stood at the end of the 2025 season, and some league names and arrangements have changed since 2021, so check an official source for the current alignment.
How the old system worked
For most of the twentieth century, the minor leagues were run by a separate organization, known in recent decades as Minor League Baseball, which held an agreement with the major leagues. That agreement, called the Professional Baseball Agreement, governed how clubs were affiliated, how players were assigned and who paid for what. Each major-league organization signed player-development contracts with a set of independently owned minor-league clubs, and those clubs paid for their own stadiums, their own staffs and part of the costs of operating.
The system had many layers. The classifications ran from Triple-A at the top, through Double-A and Class A (split into Advanced A, Class A and short-season A), to the rookie leagues at the bottom. Short-season leagues such as the New York-Penn League and the Northwest League played a summer schedule after the draft, and the Appalachian and Pioneer leagues sat at the rookie level. The Dominican Summer League and the Arizona and Gulf Coast leagues rounded out the bottom.
With about 160 affiliates and 30 major-league organizations, the average organization had a little more than five affiliated teams in the United States, and the number varied. The arithmetic is simple, but it explains the later change: the new system would average exactly four.
Why the system was reopened
The Professional Baseball Agreement was due to expire after the 2020 season. In the years before it expired, MLB had made it clear that it wanted changes: fewer clubs, better facilities, shorter bus rides and more control over the player-development process. Negotiations between the major leagues and the minor-league governing body did not produce a deal, and the coronavirus pandemic then removed the 2020 minor-league season altogether. With no games played and the agreement running out, the major leagues took the opportunity to build a new structure on their own terms.
In the winter of 2020 and 2021, MLB invited clubs to join the new system, and the invitations went to about 120 of them. The remaining clubs, about 40, were told that they would not be part of the affiliated structure. The new relationship was based on a license agreement with each club, called a player-development license, and the major leagues, not an independent body, now set the standards and ran the leagues. The 2021 season started later than usual, in May, with the new alignment in place.
The new structure: 120 clubs, four levels
The central design was simple. Each of the 30 major-league organizations would have four affiliates, one at each of four full-season levels. The levels were Triple-A, Double-A, High-A and Low-A (the last was later renamed Single-A). Rookie-level ball would continue in the complex leagues, and the old short-season levels would disappear.
| Before 2021 | From 2021 | |
|---|---|---|
| Affiliated U.S. clubs | About 160 | 120 |
| Affiliates per organization | Five or more, varying | Four full-season clubs |
| Levels | Triple-A, Double-A, Class A Advanced, Class A, short-season A, Rookie | Triple-A, Double-A, High-A, Low-A, complex leagues |
| Short-season leagues | New York-Penn, Northwest | None |
| Governing arrangement | Independent minor-league body with an agreement | MLB-run, with licenses for each club |
The names of the levels changed in a way that confuses people. In broad terms, the former Class A Advanced leagues (the California, Carolina and Florida State leagues) became Low-A, and the former Class A leagues (the Midwest and South Atlantic leagues), joined by the Northwest League, became High-A. A player who moved from Class A Advanced to Class A before 2021 would have gone down a classification. Under the new names, the equivalent move goes from Low-A up to High-A. That is why old and new descriptions of the same player can appear to contradict each other.
Triple-A and Double-A kept 30 clubs each, but their leagues were realigned under temporary names. Triple-A was reorganized as Triple-A East and Triple-A West, and Double-A became the Northeast, South and Central leagues. In 2022 the historic league names returned, including the International League and the Pacific Coast League at Triple-A and the Eastern, Southern and Texas leagues at Double-A, and the Low-A level became Single-A.
A short timeline
- Through 2020. The Professional Baseball Agreement governs affiliations, and about 160 clubs are tied to major-league organizations.
- 2020. The minor-league season is cancelled because of the pandemic, and the agreement runs out after the season.
- Winter 2020 to 2021. MLB invites about 120 clubs into a new structure and tells about 40 that they are not included.
- 2021. The new four-level structure begins play, later than usual, with six-game weeks. The draft shrinks to 20 rounds, the short-season leagues are gone and the Draft League opens.
- 2022. The historic league names return at the upper levels, and the Low-A level is renamed Single-A.
A prospect's path, before and after
The easiest way to feel the change is to follow a hypothetical player. Take a college pitcher drafted in an early round before 2021. His first summer was typically spent at a short-season club in a league such as the New York-Penn League, throwing a limited number of innings in a schedule that began after the draft. The next spring he might move to a Class A club, then Class A Advanced, then Double-A and Triple-A, so there were five or six rungs between the draft and the majors.
The same pitcher drafted after 2021 has fewer rungs. He may begin in the complex league in Florida or Arizona, or at the lowest full-season level if the club thinks he is ready, and then climb through High-A, Double-A and Triple-A. There are four full-season levels, not five, and a club that wants to see a player against better competition has fewer places to hide him. That is one reason prospect lists and promotion timetables look different than they did a decade ago.
For a fan, the practical change is that every organization now has the same shape. A player on one club's Double-A roster sits at the same level as a player at the same stage on any other club, which makes it easier to compare systems and to read transaction logs, a point worth remembering when you read a box score from a minor-league game.
What happened to the clubs left out
About 40 clubs did not receive invitations. Their fates varied, and the outcome depended on the city, the ownership and the willingness to find another league.
- Independent leagues. Several of the clubs joined independent professional leagues, which are not affiliated with any major-league club and sign their own players. MLB gave four independent leagues a formal link as Partner Leagues: the American Association, the Atlantic League, the Frontier League and the Pioneer League. The Pioneer League, which had been a rookie-level league, became one of these independent circuits.
- The Appalachian League. This long-running rookie league was reshaped into a summer league for college players using wooden bats, so the towns kept their baseball but not their affiliations.
- The MLB Draft League. A new league created in 2021 for players who are eligible for the draft, with some former New York-Penn League clubs among its members. It showcases college players in the weeks around the draft.
- Folded or relocated clubs. Some clubs ended operations or moved, and others lost their long-time relationship but kept their name and ballpark under a new arrangement.
For a fan, the practical consequence was uneven. Some towns still have professional baseball and a loyal crowd, with a different level of player and a different relationship to the major leagues. Others have a vacant ballpark or a summer team of college players. The loss mattered most in places where the club was the main entertainment in town and where the ballpark was a civic anchor.
The draft, shorter and sharper
The restructuring coincided with a change in the MLB draft. Before the pandemic, the draft ran for 40 rounds. The 2020 draft was cut to five rounds because of the circumstances, and starting in 2021 it was set at 20 rounds. The shorter draft fit the new structure: with fewer minor-league clubs there were fewer roster spots to fill.
Two knock-on effects followed. Players who would have been drafted in the 21st through 40th rounds became undrafted free agents, who can sign with any club under a bonus limit. And the shorter draft put more weight on the first rounds, where teams focus their scouting. The mechanics of the draft, including slot values and bonus pools, are explained in how the MLB draft works, and the order of selection is covered in the MLB draft lottery explained.
Facilities and the weekly schedule
A second goal of the restructuring was to improve the conditions in which players lived and worked. MLB set facility standards for the stadiums that would house affiliates, covering the areas that players use every day, such as clubhouses, training and medical rooms and the playing field and lighting. Clubs were given timelines to bring their parks up to standard, and a club that could not or would not do so risked losing its place.
The weekly schedule changed as well. The new system moved toward a standard week of six-game series, played Tuesday through Sunday with Monday off, and each series is typically against the same opponent for the whole week. The point was to reduce travel and give players a regular day of rest. It also made the schedule easier for fans to follow and let a visiting team settle into a city for a week at a time.
Parks vary a great deal. A Triple-A stadium that was built for a major-league-sized crowd is a different place from a small Single-A park in a college town, and field dimensions differ from one park to the next for historical and practical reasons. Why ballpark dimensions are all different explains why even standards leave room for variation.
How the new system pays and organizes players
The restructuring did not itself set minor-league pay, which is a separate subject covered in how minor leaguers get paid, but the two are linked. By reducing the number of affiliates, MLB centralized control of the system. Pay and conditions have remained a subject of public attention, and developments after 2021 are covered in that article.
The structure of the levels is explained in how the minor leagues are organized, and the rookie-level complex leagues, where many young players begin, are the subject of how teams use the complex leagues. The complex leagues gained importance after 2021 because short-season play ended: a recently drafted player who in an earlier year might have gone to a short-season club now often starts in the complex league in Arizona or Florida.
Supporters, critics and the open questions
The case for the restructuring rests on efficiency and player welfare. Supporters argued that a smaller system with common standards would improve facilities, cut travel and make development more consistent. Four affiliates per organization is a number clubs can staff well, and the major leagues now control the standards from top to bottom.
Critics offered a different account. They pointed to the lost teams and the communities that had supported them, the weakening of a model in which local owners ran clubs and the concentration of power in the major leagues. Some also noted that the cuts reduced the number of roster spots available to aspiring players, with fewer opportunities for those on the margins to develop.
Evidence for a verdict is incomplete. The facility standards and the six-game week are easy to describe, but whether the changes improved the development of players, or merely changed who pays for it, depends on measures that no single table can capture. A fair summary is that the restructuring delivered the standardization its authors wanted at the cost its critics described: fewer clubs and fewer towns.
Common questions
How many minor-league teams are affiliated now? 120 in the United States as of the 2025 season: four per organization, at Triple-A, Double-A, High-A and Single-A.
What happened to short-season baseball? It ended as an affiliated level. The New York-Penn League and the Northwest League were reshaped, with the Northwest League continuing as a High-A circuit.
Is the Pioneer League still affiliated? No. It became an independent league and one of MLB's Partner Leagues.
Why is Low-A below High-A when Class A Advanced used to be above Class A? Because the names were reassigned in 2021. In broad terms, old Class A Advanced is now Low-A and old Class A is now High-A, which reverses the order people were used to.
Where do recently drafted players start? Many begin in the complex leagues in Florida and Arizona, or at a full-season level if they are advanced.
Where to go next
For the current list of affiliates and results, use the minors section, and for the larger picture of how prospects move, read the minor league baseball topic page. The scoring conventions that carry across every level are in how to read a baseball box score.