Meet the MIT physicist turned Marlins coach behind the ‘torpedo’ bats used by the Yankees

NEW YORK — The New York Yankees made headlines with an explosive offensive performance against the Milwaukee Brewers on Saturday, setting a franchise record by hitting nine home runs in a single game. While their dominance at the plate was impressive, the conversation quickly shifted to the bats themselves, as several players were seen using uniquely designed lumber.

The development of these unconventional bats was the culmination of two years of research and experimentation, spearheaded by Aaron Leanhardt, a former physicist from the Massachusetts Institute of Technology who transitioned into coaching. His central question throughout this process was straightforward yet profound:

“Where are you aiming to make contact with the ball?” Leanhardt said in a phone interview on Sunday morning.

Leanhardt, now 48, first introduced this idea while working with the Yankees’ minor league hitting department in 2022. By the following season, he had advanced to the major leagues as the team’s lead analyst, where he collaborated with players such as shortstop Anthony Volpe to implement the concept in real games. According to outfielder Cody Bellinger, at least five Yankees players are set to utilize these bats early this season.

These bats, distinctive in their torpedo-like shape, are customized to align with each player’s hitting tendencies. The design ensures that the densest part of the bat is precisely where the player is most likely to make contact with the ball. Leanhardt, who recently took on a new role as a field coordinator for the Miami Marlins, explained that the goal was simple:

“It’s all about maximizing the bat’s mass and thickness in the areas where a hitter is looking to do the most damage.”

According to Major League Baseball officials, these bats comply with existing regulations. MLB Rule 3.02 mandates that bats must be smooth, round, and no more than 2.61 inches in diameter at their thickest point, with a maximum length of 42 inches. The rule also states that experimental designs require league approval before they can be used in games.

When asked if he was the sole inventor of this innovation, Leanhardt emphasized the collaborative nature of the project, crediting the input of coaches, players, MLB representatives, and bat manufacturers.

“People can distribute credit however they like,” he said. “But if anyone wants to assign me a share, I’ll gladly take it.”

Despite his humility, a Yankees official asserted that Leanhardt played a crucial role in the project’s success. Former MLB infielder Kevin Smith, who played in parts of four seasons, also acknowledged Leanhardt as the driving force behind the invention.

Leanhardt’s journey to baseball was anything but conventional. Holding a bachelor’s degree in electrical engineering from the University of Michigan and a Ph.D. in physics from MIT, he spent seven years as a physics professor at Michigan before shifting his focus to baseball coaching. His coaching career began in the independent Atlantic League in 2017, followed by a stint at a Montana community college, before joining the Yankees organization in 2018. By 2024, he was serving as the Yankees’ first-ever “major league analyst,” integrating data analysis into player performance and preparation.

His transition from academia to professional sports was driven by a love for competition and innovation.

“One of the exciting aspects of sports is how competitive it is,” he said. “Players are always looking for ways to gain an edge, and I saw an opportunity to bring my analytical background into the game to drive innovation.”

Through years of discussions with players, Leanhardt identified two primary concerns: improving contact rates and optimizing the likelihood of striking the ball with the bat’s “sweet spot”—its densest area.

“Most players will point to a location about six or seven inches from the tip of the bat and say, ‘That’s the sweet spot,’” he explained. “So, we thought, why not redistribute the weight? Take some of the excess mass from the tip and concentrate it where the best contact happens.”

Leanhardt sees minimal drawbacks to this weight redistribution strategy.

“The bat speed should remain constant, or in some cases, even improve depending on design modifications,” he said. “Ultimately, by making the barrel larger and heavier at the sweet spot, hitters can increase their chances of solid contact without compromising other aspects of their swing.”

While he refrained from discussing specific player experiences, Yankees designated hitter Giancarlo Stanton recently suggested that certain bat adjustments last season may have contributed to ligament tears in both his elbows, though he did not explicitly attribute blame. When asked about Stanton’s situation, Leanhardt declined to comment.

“That’s a question for the Yankees’ medical staff,” he stated. “I’ll defer to them on that.”

The introduction of a radically new bat design is rare in baseball history. Leanhardt noted that earlier players swung heavy hickory bats until the 1920s and 1930s, when lighter ash bats revolutionized the game. Since then, change has been slow.

“It takes the right questions and the willingness to challenge convention,” he said.

The social media buzz surrounding the bats after Saturday’s game amused Leanhardt, who acknowledged that while some players had adopted them last season, it wasn’t until this offseason that the concept gained widespread attention across the league.

“That’s why you’re seeing so many guys using them now,” he said. “Saturday’s performance just put the spotlight on it.”

Bringing these bats from concept to reality required extensive coordination. Leanhardt confirmed that he maintains close ties with MLB officials who oversee bat regulations and has direct relationships with every major bat manufacturer in baseball.

“It’s really about engaging with each company, finding the right people who understand the wood and how to shape it,” he said. “Once they see how it benefits players, they’re more inclined to produce them. That’s how momentum builds.”