Comparison of Major League Baseball and Nippon Professional Baseball

Major League Baseball (MLB) and Nippon Professional Baseball (NPB) are the highest levels of baseball in the United States and Japan, respectively. MLB started in 1876, while NPB was not formed until 1950, following reorganization of the Japanese Baseball League, which had been in existence since 1936. Though ostensibly the same game, baseball, is played in both MLB and NPB there are a number of differences between the game in the two organizations.

Game rules
The NPB rules are essentially those of the American Major League Baseball (MLB), but technical elements are slightly different.

Ball
MLB uses a standardized ball manufactured by Rawlings. Its seams are rather flat, and it is prepared for use by rubbing it with a special mud to reduce the slipperiness of the new leather. For a long period there was no standard ball in NPB, but currently a standard ball manufactured by Mizuno is used across all teams in the league. The NPB ball is slightly smaller than its MLB equivalent and has better grip, making it easier to manipulate and spin.

Field
The NPB uses a smaller strike zone, and playing field. The strike zone is narrower "inside" than away from the batter. Five NPB teams have fields whose small dimensions would violate the American Official Baseball Rules. The note set out at the end of Rule 1.04 specifies minimum dimensions for American ballparks built or renovated after 1958: 325 ft down each foul line and 400 ft to center field. Though this rule is not rigidly enforced in MLB either, where, for example, Yankee Stadium was built after 1958, opening in 2009, and does not comply with the rule, having a distance down the right field line of 314 ft and down the left field line of 318 ft.

Ties
Unlike North American baseball, Japanese baseball games may end in a tie. If the score is tied after nine innings of play, up to three additional innings will be played; this includes the playoffs, but not the Japan Series going beyond Game 7. If there is no winner after 12 innings, the game is declared a tie; these games count as neither a win nor a loss to team standings or to postseason series.

League format
MLB teams play 162 games in the regular series, while NPB teams each play 143.

The end-of-season championship in MLB is the World Series, a best-of-seven competition in which a team must win four games to clinch the title. NPB's championship is the Japan Series, also a best-of-seven competition. However, since games can end in a tie, it may take more than seven games to decide the series. If the series must be extended, all games beyond Game 7 are played with no innings limit, with Game 8 being played in the same venue as Game 7, and Game 9 and beyond played in the opposing team's venue following a moving day. A Game 8 has only happened once in Japan Series history, in the 1986 Japan Series between the Hiroshima Toyo Carp and Seibu Lions.

Rosters
MLB teams have 26-man active rosters, drawn from a larger 40-man roster of players under contract with the club. Players on the 40-man roster who are not on the active roster are typically either players currently on the injured list (or other temporary inactive list) or are assigned to the team's Triple-A minor league affiliate.

Although each NPB team roster has 28 players there is a 25 player limit for each game. Managers scratch three players before each game, typically including the most recent starting pitcher, similar to professional basketball.

Most NPB teams have a six-man starting pitcher rotation while MLB teams feature five-man rotations.

Gameplay
Unlike association football, which uses arithmetic coefficients to compare and rank the competitiveness of different leagues, no such system exists for club-level professional baseball. American MLB players, scouts, and sabermetricians have described play in the NPB as "AAAA" or "Quad-A"; less competitive than in MLB, but more competitive than in Triple-A. However, some commentators have pushed back on this characterization in recent years, suggesting that the talent level in NPB varies, with many active players who would be successful on the MLB level.

Japanese baseball is generally considered more of a contact-oriented game that American baseball; it has been said that Japanese teams practice "small ball" rather than hitting for power. However, this was questioned by FanGraphs analyst Eno Sarris in 2017, who noted that contact rates in MLB are comparable to those in NPB.

In addition, Japanese teams practice much more often than American teams; the game relies more on off-speed pitching and not as many fastballs, and team harmony is stressed over individual achievements. As American journalist Robert Whiting wrote in his 1977 book The Chrysanthemum and the Bat, "the Japanese view of life, stressing group identity, cooperation, hard work, respect for age, seniority and 'face' has permeated almost every aspect of the sport.... Baseball Samurai Style is different."

Baseball in the United States has been described as offensive while in Japan it is defensive. Because of the relative strength of pitching in the Japanese league, some have suggested that batting and fielding statistics are more influential in differentiating successful NPB teams from unsuccessful ones.