Calculating the Probability of 27 Consecutive Outs
NPB's average on-base percentage hovers around .320, meaning each batter has roughly a 32% chance of reaching base in any given plate appearance. The probability of retiring 27 consecutive batters is therefore approximately 0.68 to the 27th power, which equals about 0.015%, or roughly once every 6,700 games. With NPB playing approximately 860 games per season, the expected frequency is about once every 7.8 years. In practice, 16 perfect games have been thrown across roughly 75 years of NPB history, a rate of about one every 4.7 years. The higher-than-expected frequency is explained by the fact that ace pitchers on dominant days suppress opposing on-base percentages well below the league average.
Three Walls Against Perfection - Hits, Walks, and Errors
A perfect game can be broken by three categories of events: hits, walks, and defensive errors. Of these, only walks are fully within the pitcher's control. Whether a batted ball finds a fielder's glove or lands for a hit involves significant luck. BABIP, the batting average on balls in play, is known to be more influenced by randomness than pitcher skill. Additionally, the probability of a defense committing zero errors over nine innings is approximately 85% based on NPB averages, meaning about 15% of potential perfect games are derailed by fielding mistakes alone.
Temporal Distribution - Why Perfect Games Cluster
NPB's 16 perfect games are unevenly distributed across eras: four in the 1950s, three in the 1960s, two in the 1970s, two in the 1990s, and then a 28-year gap before Sasaki Roki's achievement in 2022. The concentration in earlier decades reflects lower batting standards and the expectation that starting pitchers would throw complete games. The 28-year drought from 1994 to 2022 coincided with improved hitting, bullpen specialization, and the trend toward pulling starters after six or seven innings. In an era where complete games themselves are rare, the prerequisite for a perfect game has become extraordinarily difficult to meet.
Sasaki Roki's Perfect Game - An Anomaly in Modern Baseball
On April 10, 2022, Chiba Lotte Marines' Sasaki Roki threw a perfect game against the Orix Buffaloes, striking out 19 batters, an NPB record for a perfect game, and recording 13 consecutive strikeouts. What made Sasaki's achievement exceptional was its structural dominance. Of 27 outs, 19 came via strikeout, meaning the defense was involved in only 8 plays. By minimizing defensive involvement, Sasaki structurally eliminated the risk of errors or unlucky hits. At 20 years old, he became the youngest pitcher in NPB history to throw a perfect game.
The Cruelty of 'One More Out'
The statistical improbability of a perfect game is underscored by the many pitchers who came agonizingly close. Yamai Daisuke of the Chunichi Dragons carried a perfect game through eight innings in Game 5 of the 2007 Japan Series before manager Ochiai Hiromitsu replaced him with closer Iwase Hitoki for the ninth. Yamai's eight perfect innings represented a probability of approximately 0.04%. The remaining three outs carried a roughly 31% success probability. Ochiai chose the certainty of his closer over the 31% chance of history. The decision remains one of the most debated in Japan Series history.
A Perfect Game Is Unrepeatable Art
No pitcher in NPB history has thrown more than one perfect game. This is not coincidence but a reflection of the event's fundamental nature: a perfect game is an unrepeatable convergence of pitching excellence, defensive reliability, opponent weakness, ballpark conditions, umpire tendencies, and pure luck. Even Sasaki Roki, with his overwhelming strikeout ability, achieved it only once. The perfect game stands as baseball's supreme individual accomplishment precisely because it cannot be engineered or replicated. Twenty-seven batters, twenty-seven outs, zero baserunners. This simple yet nearly impossible feat encapsulates everything that makes baseball endlessly fascinating.