A decade of baseball data shows the designated hitter system does not affect how teams win
As Japan's Central League prepares to adopt the designated hitter rule in 2027, new research shows that teams with skilled players win games with or without batting specialists
In the original form of baseball, all nine players bat and play defense, including the pitcher. The designated hitter system lets a team add a tenth player to the starting lineup—a specialist batter who replaces the pitcher in the batting order. The designated hitter only bats and does not play defense, while the pitcher still pitches but does not bat.
Now, researchers in Japan have analyzed 10 years (2014-2023) of game data from Japan’s Pacific League and found that the presence or absence of the designated hitter (DH) system does not change the relationship between player talent and winning. Published in PLOS One, the study also presents a new method to measure player contributions by using performance data to compare starting players with backup players at each position.
Evaluating the impact of rule changes in baseball
The DH system was introduced in Major League Baseball in the United States in 1973 and was adopted by the Pacific League in Japan in 1975. Japan’s Central League plans to adopt the DH rule in 2027.
The system was introduced to make games more exciting with better hitting and higher scores, which would bring in more fans. It also helps pitchers by decreasing their workload and the risk of injuries because they do not have to bat. However, people debate whether it oversimplifies the game or decreases strategic decision-making by managers.
Researchers from Nagoya University's Graduate School of Informatics analyzed team performance and how much each player contributes to winning through batting, fielding, and pitching actions during games, in cases with and without the DH system.
The Pacific League has been considered the stronger of Japan’s two leagues, with some crediting this to the DH system. However, statistical analysis showed no significant difference in how player performance influenced wins, whether the DH was included or not.
Developing a more accurate measure of player value
The research team developed an improved method to determine player value. To understand how starting players contribute to winning games, they compared them with the performance of backup players who would replace them.
“We used the WAR (Wins Above Replacement) framework, but the traditional method uses the same mathematical baseline for all positions,” explained Yasuhiro Suzuki, associate professor and coauthor.
“In reality, performance varies significantly according to position. For example, players at defensive positions, such as catchers, are weaker hitters than those at offense-heavy positions, such as first base. We measured both starting and backup performance at each position using actual game data to better reflect position-specific differences in player value.”
They also tracked designated hitters as their own category because they only bat and never play defense. This approach let them accurately compare winning patterns with and without the DH rule.
This is the first study to use the WAR framework to examine DH impact on team success. Previous studies focused on injuries and pitching strategies.
Implications for Japan and beyond
As a baseball fan and statistics researcher, first author and master's student Shino Shimizu wanted to understand if rule changes affect the fundamental dynamics of the game. “Our findings suggest that while the DH rule changes the game experience, it doesn't alter baseball's fundamental competitive balance because teams with better players still win,” she said.
The researchers focused on data from the six teams in the Pacific League, but their method can also be applied to Central League teams to predict how the DH adoption will affect performance and to identify potential advantages and disadvantages.
Major League Baseball adopted the universal DH system in 2022, making understanding its impact increasingly important worldwide. This study provides evidence for similar debates happening across baseball leagues globally.
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Now, researchers in Japan have analyzed 10 years (2014-2023) of game data from Japan’s Pacific League and found that the presence or absence of the designated hitter (DH) system does not change the relationship between player talent and winning. Published in PLOS One, the study also presents a new method to measure player contributions by using performance data to compare starting players with backup players at each position.
Evaluating the impact of rule changes in baseball
The DH system was introduced in Major League Baseball in the United States in 1973 and was adopted by the Pacific League in Japan in 1975. Japan’s Central League plans to adopt the DH rule in 2027.
The system was introduced to make games more exciting with better hitting and higher scores, which would bring in more fans. It also helps pitchers by decreasing their workload and the risk of injuries because they do not have to bat. However, people debate whether it oversimplifies the game or decreases strategic decision-making by managers.
Researchers from Nagoya University's Graduate School of Informatics analyzed team performance and how much each player contributes to winning through batting, fielding, and pitching actions during games, in cases with and without the DH system.
The Pacific League has been considered the stronger of Japan’s two leagues, with some crediting this to the DH system. However, statistical analysis showed no significant difference in how player performance influenced wins, whether the DH was included or not.
Developing a more accurate measure of player value
The research team developed an improved method to determine player value. To understand how starting players contribute to winning games, they compared them with the performance of backup players who would replace them.
“We used the WAR (Wins Above Replacement) framework, but the traditional method uses the same mathematical baseline for all positions,” explained Yasuhiro Suzuki, associate professor and coauthor.
“In reality, performance varies significantly according to position. For example, players at defensive positions, such as catchers, are weaker hitters than those at offense-heavy positions, such as first base. We measured both starting and backup performance at each position using actual game data to better reflect position-specific differences in player value.”
They also tracked designated hitters as their own category because they only bat and never play defense. This approach let them accurately compare winning patterns with and without the DH rule.
This is the first study to use the WAR framework to examine DH impact on team success. Previous studies focused on injuries and pitching strategies.
Implications for Japan and beyond
As a baseball fan and statistics researcher, first author and master's student Shino Shimizu wanted to understand if rule changes affect the fundamental dynamics of the game. “Our findings suggest that while the DH rule changes the game experience, it doesn't alter baseball's fundamental competitive balance because teams with better players still win,” she said.
The researchers focused on data from the six teams in the Pacific League, but their method can also be applied to Central League teams to predict how the DH adoption will affect performance and to identify potential advantages and disadvantages.
Major League Baseball adopted the universal DH system in 2022, making understanding its impact increasingly important worldwide. This study provides evidence for similar debates happening across baseball leagues globally.
END