The Moment He Stands on First Base, the Atmosphere in the Stadium Changes

In the bottom of the seventh inning, number 62 bursts out of the bench to replace a batter who reached base with a hit. The moment Kōnosuke Tatsumi puts on his helmet and steps onto first base, the timing of the opposing battery is slightly disrupted. The pitcher becomes conscious of the quick motion, the catcher prepares for a throw to second base, and the infielders make minor adjustments to their positions. He hasn’t even started running yet. Even without moving, the defensive setup is already beginning to crumble.

Kōnosuke Tatsumi of the Hiroshima Toyo Carp has recorded 25 stolen bases as a pinch runner, tying the Japanese record for stolen bases by a pinch runner set by Shiro Fujise of the Kintetsu Buffaloes in 1979. This marks a milestone not seen in 45 years—yet behind this number lies more than just individual speed. The result is a combination of the team’s design to establish a ‘player who just runs’ as a viable asset and Tatsumi’s meticulous management of his own body.

This article will explore Tatsumi’s 25 stolen bases through the lens of the question, ‘Who does this make easier?’

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Zero Stolen Bases with Rakuten—The Gap Between ‘Fast Player’ and ‘Player Who Can Steal’

Tatsumi joined Rakuten in the 2020 developmental draft. His speed, clocked at 5.8 seconds for 50 meters, was well-known even then, but his opportunities in the first team were limited over three years, resulting in zero stolen bases. He had speed, but there exists a gap in the system between being ‘fast’ and being ‘able to steal.’

Having a player specialized in pinch running on the bench means dedicating a roster spot solely to ‘running.’ To justify this spot, the batting lineup must be designed to consistently create situations where a pinch runner can be sent in. Furthermore, a game plan for the late innings must include the order of defensive substitutions and pitching changes; otherwise, it ends up being just ‘a fast player sitting on the bench.’ What Tatsumi lacked during his time at Rakuten was not speed, but rather the team’s circuitry to activate that speed.

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Hiroshima’s Circuit for Making Pinch Running Viable

In the offseason of 2023, Tatsumi transferred to Hiroshima. What changed was not his running ability, but rather the team’s approach to constructing games with the premise of utilizing his legs.

Looking at Hiroshima’s usage patterns, Tatsumi is primarily brought in as a pinch runner in the later innings, often in close situations with a one-run lead or tie. In other words, the bench is calculating the scenarios that would lead to ‘bringing in Tatsumi’ as they manage the game. The timing of the starting pitcher’s replacement, the order of pinch hitters, and the arrangement of defensive substitutions—all are interconnected around Tatsumi’s pinch running.

Here, Tatsumi’s stolen base success rate is crucial. Reports indicate that his success rate exceeds 80%. When he comes in as a pinch runner, he advances to second base with high probability. This means that there is no need to use a bunt to move the runner from first to second. The batter can focus on hitting instead of bunting. By running, Tatsumi makes it ‘easier’ for the next batter.

Moreover, if the pitcher frequently uses quick motions out of concern for stolen bases, the accuracy of their breaking balls may decline. If the catcher is focused on throwing to second base, even a moment’s hesitation can occur when handling a one-bounce throw. Just by being on first base, Tatsumi narrows the options for the opposing battery—functioning even without running. This is the essence of ‘specialized pinch running as a system.’

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3% Body Fat, Four Types of Supplements—Designing the Body as a ‘Tool’

Tatsumi’s body management is at a level that could be described as somewhat unusual. With a body fat percentage of 3% and a weight of 65 kg, he reportedly takes four types of supplements daily to maintain these numbers. The monthly cost for supplements amounts to several tens of thousands of yen—resulting in an annual self-investment of several hundred thousand yen.

A body fat percentage of 3% is a level typically reached temporarily by bodybuilders just before competitions, and maintaining it year-round requires significant nutritional management for an athlete. Tatsumi’s focus on this number is to optimize his body for the singular function of ‘running.’ He sheds excess weight and maximizes the response for acceleration and deceleration. This philosophy of body design is fundamentally different from that of players who are required to demonstrate overall skills in hitting and fielding.

In interviews, he has expressed a desire to create a state where he can control his body as he wishes. This statement reflects an awareness of viewing base running not as a ‘talent’ but as a result of ‘skill and management.’ A body fat percentage of 3% is not merely a result; it is part of the blueprint.

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What the Breakdown of 25 Stolen Bases Reveals—The Precision of ‘When to Run’

I would like to further dissect the figure of 25 stolen bases as a pinch runner. Being specialized in pinch running means that opportunities to participate are inherently limited. Unlike a starter running around for nine innings, a pinch runner may only get one chance in a game, and there may be days without any opportunities at all. The fact that he has succeeded 25 times within these limited chances indicates an extremely high precision in the judgment of ‘when to run.’

Stolen bases cannot be achieved by speed alone. It involves instantaneously reading multiple variables, such as the pitcher’s motion habits, the catcher’s arm strength and time to throw, the tendencies of pitch distribution by count, and signals from the bench. When Tatsumi runs, his judgment is a blend of data analysis from the bench and his own experiential knowledge. The moment when individual intuition aligns with team information—that is the first step to a successful stolen base.

The precision of data analysis, the technology of pitchers’ quick motions, and the catchers’ throw times have all significantly evolved since Shiro Fujise set the record in 1979. The weight of reaching the same number amid 45 years of evolution in the defensive side’s ‘system to prevent stolen bases’ cannot be measured by simple comparison.

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Is ‘Specialized Pinch Running’ a New Position?—The Structure that Utilizes People

Observing Tatsumi’s success naturally leads to the question of whether the role of ‘specialized pinch runner’ will increase in the future. However, I would like to pause for a moment.

For specialized pinch running to be viable, several conditions must be met. First, there must be the luxury of dedicating one roster spot solely to running—meaning there are players who can fulfill multiple roles in other positions. Next, the bench must be capable of calculating scenarios to send in a pinch runner. Finally, there must be a design for the late innings that includes defensive substitutions after the pinch running. These are discussions on a different dimension than whether the pinch runner is excellent.

In other words, Tatsumi’s 25 stolen bases were not achieved because ‘there was a fast player,’ but rather because ‘the team had a system to utilize a fast player.’ This order must not be reversed.

The Hiroshima team has cultivated an awareness of base running within a tradition that emphasizes mobility, a data analysis system, and a coaching staff’s design for utilization—these accumulations have translated into numbers through the legs of one player, Tatsumi. When individual effort aligns with the system, records are born.

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Who Benefits from Running?

Finally, let’s return to the initial question: ‘Who does this make easier?’

When Tatsumi runs, the next batter does not need to bunt. The pitcher is forced into quick motions, disrupting their natural pitching rhythm. The catcher must simultaneously manage awareness of the runner and pitch to the batter. In other words, just by being on first base, Tatsumi makes it easier for his teammates while gradually increasing the pressure on the opponents.

The role of a specialized pinch runner does not leave behind batting averages or home runs in the scorebook. There are hardly any defensive innings. Yet, it generates ‘pressure’ that changes the flow of the game and reduces the burden on teammates. Subtle arrangements lead to flashy scores. That is the structure.

Kōnosuke Tatsumi, with a body fat percentage of 3%, spending tens of thousands of yen monthly on supplements, and achieving 25 stolen bases as a pinch runner. When viewed solely through numbers, it may seem extreme. However, behind that extremity lies a system designed to establish a single role and the quiet resolve of a player who continues to refine his body within that system.

Just running—please take a moment to consider the depth of the structure that supports that ‘just.’