How Umpires Are Trained, Assigned and Evaluated
How an umpire gets from an umpiring school to a major-league crew of four, what each position does, how crews and postseason assignments are made, and how umpires are graded.
A major-league umpire is the product of one of the longest apprenticeships in sports. Almost nobody walks into the job. The typical path runs through a professional umpiring school, then several years of work in the lowest minor leagues, then a climb through the levels of the minors, then years more as a fill-in who covers vacations and injuries, and only then a full-time place on a major-league crew. The result is a group of roughly seventy people whose calls decide close games in front of tens of thousands of fans and, in the postseason, millions of television viewers.
This article explains how that system works: the training path, the four positions on the field and what each umpire is responsible for, how crews are put together and sent to ballparks, how postseason assignments are decided, and how umpires are evaluated. Where details change from year to year, such as the use of technology to check balls and strikes, the text says "as of the 2025 season" and points to MLB's own announcements, because this is the kind of rule that is revised often.
The path from umpire school to the majors
The first step is an umpiring school. A small number of professional schools, among them one in Florida that has trained umpires for decades, run courses of several weeks that cover the rulebook, field mechanics (where to stand, how to move, how to signal), plate work and written tests. Students are graded, and the best performers are offered jobs in the lowest levels of professional baseball. The rest go home with an education in the rules and a lesson in how competitive the field is: far more people attend than ever work a professional game.
The job offers come at the entry levels of the minors, the complex and rookie leagues, where games are played in front of small crowds and an umpire may work with only one or two colleagues. From there the path runs upward: Single-A, Double-A, Triple-A. At each stage the umpire is evaluated, and promotion depends on ratings, openings and timing. The number of major-league positions is small and changes only when an umpire retires, resigns or is released, so progress depends partly on talent and partly on vacancies. It is common for the climb to take many years.
The minor leagues that umpires climb through were reorganized in 2021, a change described in the 2021 minor league restructuring. At the top, umpires are employed by Major League Baseball and are not part of any club's staff, which is why they can be assigned to any series. Until 1999 the American and National Leagues kept separate umpire staffs; they were combined in 2000, so a single crew can work an American League game one night and a National League game the next.
The fill-in years
The step between Triple-A and a full-time job is a long one. Major-league umpires take vacation during the season and are sometimes injured or ill, and when a crew has an opening, a Triple-A umpire fills in. A fill-in is, in effect, an audition: he works with experienced colleagues, often on short notice, and the evaluators watch. Some umpires work as fill-ins for years before a vacancy gives them a permanent place.
The result is a structure with two layers: the full-time umpires, and a group of call-ups who are close and waiting. The distinction matters for accountability, because a poor evaluation can close the door to a full-time job, and a good one can open it sooner than the calendar would suggest.
The four positions and what each umpire does
A regular-season crew has four umpires, one for each of four stations: home plate, first base, second base and third base. The rulebook gives the plate umpire the title of umpire-in-chief, and he has the responsibility for the flow of the game, including calling balls and strikes, ruling on whether batted balls near the plate are fair or foul, and making calls on plays at home.
| Position | Main responsibilities |
|---|---|
| Home plate | Balls and strikes, fair or foul near the plate, plays at the plate, tags, catch-or-trap calls on short fly balls, the lineup exchange |
| First base | Plays at first base, fair or foul down the right-field line, appeals on checked swings by right-handed hitters |
| Second base | Plays at second base, covers shallow outfield balls, moves to cover bases as plays develop |
| Third base | Plays at third base, fair or foul down the left-field line, appeals on checked swings by left-handed hitters |
The important fact about the positions is that they are not fixed. Umpires move on the field, depending on where the runners are and where the ball is hit, to get the best angle on the play. Their positioning is called mechanics, and it is taught in schools and reviewed in evaluation. With a runner on first base, for example, the base umpires take positions that differ from those used with the bases empty, so that no play is left without an umpire close enough to see it. When a ball is hit to the outfield, the crew shifts to cover the bases, so that the umpire who started at first base may end up at second or third. These rotations are among the details that spectators rarely notice and umpires practice constantly.
The crew's positions also rotate from game to game, so each umpire works the plate about once every four games and the bases on the other days, and the burden of calling balls and strikes is shared. Working the plate is the hardest job: the umpire crouches behind the catcher, watches close to three hundred pitches in a typical game, and is the center of attention for most managerial arguments. The base umpires have lighter loads but have to react to a play that can happen in half a second and in a position where the angle may be poor.
Crews of four, and crews of six
The standard crew in the regular season has four umpires. One veteran umpire is named crew chief by MLB, with seniority a factor but not the only one, and he is the authority for the group, runs the pregame meeting and has the final say within the crew. The chief does not outrank the others in terms of calls on the field. He leads the crew's discussions, goes to the replay headset when a play is reviewed, and is the person who settles questions about how the crew will handle a situation.
In the postseason the crew expands to six, with two extra umpires stationed along the outfield foul lines. The additional umpires help rule on fair and foul balls near the lines and on catch-or-trap plays that the base umpires cannot see well. The rule about fair and foul batted balls, discussed in the rules of fair and foul balls, is the main reason for the extra people: a ball that clips the line in the corner is hard to call from the infield. The All-Star Game also uses a six-man crew assembled from umpires chosen for the event.
At lower levels the number of umpires is smaller: many minor-league games are called by crews of three or fewer, and amateur games by one or two. Two-man and three-man systems have their own mechanics, and an umpire moving up learns to use a four-man crew, not just to join one.
How crews and series are assigned
MLB's umpiring department makes the assignments. The full-time umpires are placed in crews of four, and a crew then works a series, usually of three or four games, in one city before moving to the next. The details of how the sequence is built are not published, and readers who need them should look to MLB's own statements.
Two practical realities shape the process. First, travel: a crew moves with the teams, which means a long series of plane trips with few days off. Second, vacations: each umpire takes time off during the season, so the crew with an absent member is filled by a call-up from Triple-A. The result is that the crew on the field in July may not be exactly the one that was there in April.
Postseason and special assignments
The postseason is where assignments are most visible, and they are made by merit. Umpires earn their way into October by rating well in evaluations through the year, and the crews for the postseason are assembled from the umpires who rated highest, so the group calling a division series is a selected one, not an ordinary crew promoted. Being chosen for the World Series is regarded as one of the main honors of the profession, and the reverse is also true: an umpire who has a poor year can miss the postseason.
The details of the rating process are not public, and MLB describes it only in general terms. The principle, though, is consistent with every other part of the system: umpires advance on performance, and the evaluation process is the means.
How umpires are evaluated
There are three main evaluation tools. The first is in-person observation by supervisors who attend games, watch from the stands or the dugout area and write reports on mechanics, communication, game management and the handling of arguments. The second is the review of ball-and-strike calls against ballpark tracking systems. Since the early 2000s, MLB has measured whether called balls and strikes match the strike zone as the rulebook defines it, with tracking systems that have become more precise over time. The measurements are used to grade plate umpires and to identify consistent errors. The third is video: umpires review their own plays, and the league reviews them too.
The strike zone, for reference, is defined in the rulebook as the area over home plate between a line at the midpoint between the top of the batter's shoulders and the top of the uniform pants and a line at the hollow beneath the kneecap. That is the standard the tracking systems compare against, and the rulebook should be checked for the current wording. The task is difficult: the plate umpire has to judge a ball that is moving at high speed, often curving, and crossing a zone that is three-dimensional and varies with each batter's stance. Even the best umpires miss some pitches, by inches.
Two other developments bear on evaluation. Replay review, introduced in 2014, lets managers challenge a set of calls, and the crew chief goes to a headset connected to a review center in New York. Replay reviews calls on the bases, home runs and many plays at the plate, but not balls and strikes. And automated ball-strike systems, which could remove the human judgment on pitches, were tested in the minor leagues and in spring training for several seasons, including a version in which a player can challenge a call. Through the 2025 season, balls and strikes in the regular season were still called by the plate umpire without that technology. Beginning in 2026 MLB uses a challenge version: the plate umpire still calls every pitch, but the batter, pitcher or catcher may challenge a call immediately, each team has two challenges per game and keeps one when it wins, and the tracking cameras decide. Readers should check MLB's current rules for further changes. The subject is covered in automated ball-strike systems and how robot umpires are tested.
What happens before and during a game
The crew's work begins before the first pitch. The umpires arrive well ahead of time, hold a pregame meeting to go over the day's responsibilities, and check the field, including the condition of the grass and dirt, the lines and the bases. The plate umpire takes the lineup cards from the managers at home plate, which formally begins the game. The umpires also inspect equipment, a subject covered in the rules for bats, balls and gloves, and they prepare new baseballs with a special mud so that the pitcher can grip them.
During the game, umpires apply the rules as written, with judgment calls on checked swings, tags, force plays and interference. They also manage conflict. Ejections and arguments explains the procedure for ejecting a manager or a player, and baseball's unwritten code also shapes how players and managers deal with umpires, as the unwritten rules of baseball explains. Some rules are only enforced if a team asks: batting out of turn and other rare rules describes appeals that the umpire will not make himself.
Why it matters beyond the field
Because umpires affect scoring, their work interests people outside the stadium too. The plate umpire's habits can influence how many walks and strikeouts a game contains, and some bettors and analysts study umpire tendencies when thinking about total runs. Moneyline, run line and totals explained shows what a total is and how it is priced, and it is a good place to start for anyone curious about the link. Betting involves a risk of loss, is for adults of legal age where it is legal, and anyone who feels a problem developing can call 1-800-GAMBLER for free confidential help.
Common questions
How many umpires are on the field in a major-league game? Four in the regular season, one at each of home plate and the three bases. In the postseason the crew is six, with two additional umpires on the outfield foul lines.
Who is the crew chief? A veteran umpire named by MLB to lead the crew, who leads the pregame meeting and goes to the headset when a play is reviewed.
Can a call be appealed to another umpire? In certain cases, yes: a plate umpire can ask a base umpire for help on a checked swing, and an umpire can seek help from colleagues on a ruling. Balls and strikes are the plate umpire's call, subject since 2026 to the automated challenge described above.
Are umpires employed by the teams? No. They are employed by Major League Baseball and assigned to crews, which is why they have no ties to individual clubs.
Does replay review cover balls and strikes? No. Replay review does not, though since 2026 a separate automated challenge system can overturn a called pitch.
Do umpires rotate positions? Yes. Within a crew, each umpire takes a different position from game to game, so everyone works the plate in turn.
Where to go next
For the rules that umpires apply every day, start with the rules of fair and foul balls and the rules for bats, balls and gloves. To see which umpires are on a given day, check the scores page for the day's games and the schedule for upcoming series, and browse the rules and umpiring topic page for news on rule changes and technology.