The Official (and Unwritten) Rules You Probably Didn't Realize MLB Players Follow

According to sports writer Hal McCoy, players can wear their hats however they'd like while not playing (like during interviews, batting practice, etc.). When it gets to game time, though, all hats must face forward. The first team to adopt the hat trend in the first place? The New York Knickerbockers, who reportedly began wearing straw hats in 1849. A more traditional take on the baseball cap made its debut in the late 1850s and has since evolved into today's baseball cap.

Catchers and players participating in the Home Run Derby have been permitted to wear their hats backward, as Ken Griffey Jr. notably did throughout his career.

Some players opt for a double ear-flap helmet, while others prefer the mandated single ear-flap helmets that only cover the ear facing the pitcher. When it comes to the minor leagues, things get a little stricter: Minor league players must wear double ear-flap helmets.

That's because, according to the official rules, any exposed part of a player's undershirt must be a solid team color. League-wide exceptions are made for occasions like Mother's Day, when players sport pink to honor moms.

They're the only players who aren't allowed to have "numbers, and/or letters, insignia attached to the sleeve of the undershirt," likely because it could be considered distracting for opposing players at bat.

Okay, MLB's rulebook does not explicitly state that players must wear belts, but the rules do say that all players must wear a uniform identical in style. Every single MLB team's uniform currently includes a belt, so it looks like they're here to stay!

Some players, like Ronald Acuña, prefer to layer up their necklaces, while others wear simple chains. Diamonds on the field can pose a risk though: In a 2018 game, Yoenis Cespedes broke his necklace while sliding into second base, leaving sparkling gems scattered across the field.

In 2019, MLB changed the rules around cleats to allow for more vibrant styles that express player individuality. Prior to this, at least 51 percent of a player's cleat had to feature one of their team's primary colors. Now, cleats can feature black, white, gray, any uniform colors, or any additional colors approved by individual teams.

According to the official rulebook, anyone who wishes to be on the field must be in uniform, including coaches. In fact, the official definition of a coach is as follows: "A team member in uniform appointed by the manager to perform such duties as the manager may designate, such as but not limited to acting as base coach."

Managers, on the other hand, are not required by the rules to dress in uniform—but as tradition has it, they do.

While MLB rules states, "Players of opposing teams shall not fraternize at any time while in uniform," that rule is seldom followed.

Okay, maybe that's dramatic, but it's sort of true! A player's baseball age, typically used in the media, notes how old he is as of July 1 during the season. It establishes one age for the player for the entire season—and it doesn't change, even if he celebrates a birthday. Bryce Harper, for example, turned 31 on the day of 2023's NLCS Game 1 pictured here, but the game was considered to be in his age-30 season.

Who knew MLB had so many unwritten rules that nearly every player follows—and one of the biggest ones? If a player is hit by a pitch, he's supposed to remain even-keeled and not rub the spot where the pitch hit. "There is a code of masculinity that exists in this game," former catcher John Baker said in 2012.

Another unwritten rule establishes the expectation that players walk behind the catcher and umpire when approaching the batter's box. According to MLB writer Anthony Castrovince, it's a "matter of etiquette."

In 2023, MLB released several new rules designed to make the game more efficient. One of the biggest was the introduction of a pitch clock. Pitchers now have 15 seconds to throw a pitch when bases are empty and 20 seconds when there are runners on base. So, what happens when the pitch isn't released in time? The pitcher is charged with a ball.

If a batter isn't in the box and ready to swing within eight seconds remaining on the clock, he will receive a strike. No player is immune—not even beloved former Dodger Cody Bellinger, who received a violation after a standing ovation.

They can ask for a new ball in the middle of an inning, but they must do it with at least eight seconds left on the pitch clock. According to ESPN, if a player requests a new ball several times in a row, it might result in a warning at the discretion of the umpire.

As the official rules state, "He shall remain in the clubhouse or change to street clothes and either leave the park or take a seat in the grandstand well removed from the vicinity of his team's bench or bullpen." That's right–they can technically take in the rest of the game from the stands if they so choose. What they can't do? Reenter the dugout in disguise, as Mets manager Bobby Valentine did in 1999, resulting in a two-game suspension and a $5,000 fine.

Should an ambidextrous pitcher take the mound, he must reveal which hand he'll be pitching with before the batter reaches home plate. Wearing his glove on his non-throwing hand typically does the job. He is not allowed to switch hands until the batter is out, reaches a base, or benched for a pinch-hitter.