Japan rules

Japan’s game is virtually the same as what you get anywhere but there are rule and format differences that make the game slightly different. Here are some of those that influence the game one sees on the field.

Rules on the field of play

Automatic ejection

There are two automatic ejections in NPB:

  • Hitting a batter in “the area of the head” is declared a dangerous pitch (危険球-“kikenkyu” and results in the automatic ejection of the pitcher.
  • Arguing a call for more than three minutes.

Arguing balls, strikes and balks, however, does not mandate an ejection.

The “collision” rule

This rule is used in lieu of obstruction at home plate. A runner is safe if a fielder obstructs the basepath near home plate, whether or not he has the ball. A runner is out if he initiates contact with a fielder when attempting to score.

Pitcher warm-up

Pitchers are permitted to warm up in foul territory while their team is at-bat. Prior to the start of the inning, pitchers have one minute to make up to eight warm-up pitches.

Video ‘request ‘system

For some reason NPB opted to name video challenges requests. Managers are allowed up to two failed challenges through the first nine inings and are given another in extra innings. To signal a request they draw a square with both hands in the air, symbolizing a TV set as rugby referees do when requesting a ruling from their television match officials. The following cannot be challenged:

  • Balls, strikes, checked swings, and batted balls striking the batter
  • Obstruction and interference
  • Infield flies
  • Batted balls within the infield
  • Balks

The umpiring crew, with the exception of the umpire making the call, will go under the stands to view the plays on a TV feed, often on a tiny, substandard monitor and issue a decision within five minutes.

Balks — and the ‘3 second rule’

Balks will also be called on pitchers who fail to come to a complete stop for at least three seconds before coming to the plate.

Game length

Games are called after 12 innings. Any game tied after five innings when it is called is declared a tie. Until 2011, PL games could be suspended due to darkness, light failure, a team’s travel needs or for security reasons. Since 2012, NPB has not permitted suspended games.


Tie games are ignored in winning percentage calculations, although from 1956 to 1961 the CL counted ties as half a win and half a loss, while the PL did so from 1956 to ’58 and again in 1961.


Unearned runs

Once unearned run, always unearned. If a runner on third scores on an errant pickoff throw, the run will remain an unearned run even if the next batter reaches on a base hit that would have scored the runner without the error.


The active roster

Managers select 25 of their 29 active players to be suited for the game. Those and game coaches, trainers, and interpreters are the only ones eligible to be on the bench. Up to four imported players may be on the active roster, with a maximum of three position players or pitchers.

See HERE for more on import player rules.

Activation and deactivation

Any player on the 70-man organizational roster can be promoted to the active roster provided he has not been deactivated within the past 10 days. There are no options limiting how many times a team can deactivate a player. Players on the active roster earn service time toward free-agent eligibility whether they are included in the 25-man game roster.

Roster deadline

The deadline to add new players to the 70-man roster is now July 31, although players claimed on waivers may be added after that.

Developmental contracts

Players on developmental contracts do not count against a team’s 70-man roster and the only official games in which they can play are with each club’s farm team. Some teams have “third teams” which play against amateur and unaffiliated minor league teams.

writing & research on Japanese baseball