# MLB uniforms question

**URL:** <https://boards.straightdope.com/t/mlb-uniforms-question/1029373>\
**Category:** The Game Room\
**Tags:** baseball-mlb\
**Created:** [April 19, 2026, 1:07am UTC](https://boards.straightdope.com/t/mlb-uniforms-question/1029373 "2026-04-19T01:07:23Z")\
**Posts on this page:** 4\
**Page:** 1

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**Author:** ![mixdenny](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/mixdenny/32/2962_2.png) [@mixdenny](https://boards.straightdope.com/u/mixdenny)\
**Post date:** [April 19, 2026, 1:07am UTC](https://boards.straightdope.com/t/mlb-uniforms-question/1029373/1 "2026-04-19T01:07:23Z")

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The rules for uniforms contains the following paragraph:

“If the undershirt is exposed then all the players on the team must wear matching ones. Numbers or other devices may be worn on the sleeve of the undershirt (for example, if it is worn with a sleeveless jersey), except that pitchers may not have such devices on their undershirt sleeves”."

hat is the reason for this rule?

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**Author:** ![kenobi\_65](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/kenobi_65/32/13178_2.png) [@kenobi\_65](https://boards.straightdope.com/u/kenobi_65)\
**Post date:** [April 19, 2026, 1:08am UTC](https://boards.straightdope.com/t/mlb-uniforms-question/1029373/2 "2026-04-19T01:08:43Z")

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I would guess that such “devices” (graphics) on the pitcher’s pitching arm could be distracting to the batter as the pitcher delivers.

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**Author:** ![dolphinboy](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/dolphinboy/32/330_2.png) [@dolphinboy](https://boards.straightdope.com/u/dolphinboy)\
**Post date:** [April 19, 2026, 1:28am UTC](https://boards.straightdope.com/t/mlb-uniforms-question/1029373/3 "2026-04-19T01:28:27Z")

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I can’t think of any other reason…

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**Author:** ![kenobi\_65](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/kenobi_65/32/13178_2.png) [@kenobi\_65](https://boards.straightdope.com/u/kenobi_65)\
**Post date:** [April 19, 2026, 2:45am UTC](https://boards.straightdope.com/t/mlb-uniforms-question/1029373/4 "2026-04-19T02:45:05Z")

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This article speculates that distraction is the reason why.

> [@](#):
>
> ## The undershirt rules get stricter for pitchers.
> 
> 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.

> **[The Really Specific Official (and Unwritten) Rules MLB Players Must Follow](https://www.menshealth.com/entertainment/g60080397/rules-mlb-players-follow/)**
>
> They don't HAVE to wear caps—but there's a catch.