NEW YORK — The New York Yankees’ bats were the talk of the town after the team’s historic nine-home run performance against the Milwaukee Brewers on Saturday. The conversation then shifted to the unconventional bats used by some players in the 20-9 victory.
The specially designed bats are the outcome of two years of research and experimentation led by a former physicist from the Massachusetts Institute of Technology who is now a coach.
The main question at hand?
“Where are you aiming to hit the ball?” explained Aaron Leanhardt during a phone interview on Sunday. “Where do you want to make contact?”
Leanhardt, 48, started this project while working in the Yankees’ minor-league hitting department in 2022 and introduced it to the big leagues last season as the team’s lead analyst. Some players, such as shortstop Anthony Volpe, tested these bats in games. This season, up to five Yankees players are expected to use them, according to outfielder Cody Bellinger.
These bats, with their streamlined shape, are customized to each player’s preferences and are engineered in a way that ensures the densest part of the bat aligns with where the hitter commonly makes contact with the ball, Leanhardt explained. During the offseason, he transitioned to a field coordinator role with the Miami Marlins.
“Essentially,” he said, “the goal is to maximize the weight and size of the bat in the area where you’re looking to do the most damage to the baseball.”
Anthony Volpe (holding a “torpedo” bat) congratulates Jazz Chisholm during the Yankees’ 20-9 win on Saturday. (Mike Stobe / Getty Images)
A spokesman for Major League Baseball informed The Athletic that these bats comply with league regulations. MLB Rule 3.02 specifies that a bat must be a smooth, round stick not exceeding 2.61 inches in diameter at its thickest point and not longer than 42 inches. It also states that “experimental” bats cannot be used unless approved by MLB.
When asked if he was the mastermind behind this technology, Leanhardt credited the collaborative effort involving coaches, players, MLB, and bat manufacturers.
“The recognition goes to those who deserve it,” Leanhardt noted. “But if credit needs to be attributed, I’m happy to take a share.”
However, a Yankees official praised Leanhardt, saying he deserves “a lot” of credit. Retired infielder Kevin Smith, who played in the majors for four seasons, also acknowledged Leanhardt as the inventor.
Yes, the Yankees have a literal genius MIT Physicist, Lenny (who is the man), on payroll. He invented the “Torpedo” barrel. It brings more wood – and mass – to where you most often make contact as a hitter. The idea is to increase the number of “barrels” and decrease misses. pic.twitter.com/CsC1wkAM9G
— Kevin Smith (@KJS_4) March 29, 2025
Leanhardt’s journey to baseball was unconventional. He holds a bachelor’s degree in electrical engineering from the University of Michigan and a Ph.D. in physics from MIT. He taught physics at the University of Michigan from 2007 to 2014.
In 2017, Leanhardt began coaching in the Atlantic League and later at a Montana community college before joining the Yankees in 2018. In the 2024 MLB season, he served as the team’s first “major league analyst,” responsible for integrating quantitative data with on-field performance.
What prompted his shift from academia to baseball?
“One of the appealing aspects of sports is its competitiveness,” Leanhardt explained. “Players are eager to push boundaries, and it gave me the chance to apply my expertise in an innovative way.”
Through conversations with players, Leanhardt noted two primary concerns: increasing contact with pitches and hitting the ball more consistently with the bat’s sweet spot – the densest area.
“Players often point to a spot on the bat about six or seven inches below the tip, where the sweet spot typically exists,” he stated. “From these discussions emerged the idea of reallocating the weight on the bat – putting more weight where you aim to make contact while reducing weight at the sweet spot. That was the initial concept. The goal was to concentrate the mass where it matters most and optimize performance.”
Leanhardt emphasized that there are minimal downsides to redistributing the bat’s weight.
“Bat speed should remain consistent,” he assured. “There may even be a slight increase in bat speed with a redesigned bat. Ultimately, by enhancing the weight and size at the sweet spot, players can potentially improve performance without sacrificing other qualities.”
Leanhardt declined to discuss individual players’ experiences with the new bat. Yankees designated hitter Giancarlo Stanton previously suggested that adjustments to his bat last season may have contributed to ligament tears in both elbows that landed him on the injured list, although he did not place blame. When asked about Stanton’s situation, Leanhardt deferred to the Yankees’ medical staff.
“For inquiries regarding that, please consult the Yankees’ medical team,” he stated. “I trust their expertise in such matters.”
Leanhardt acknowledged that it typically takes time for a radically new bat design to gain traction in the industry.
“In the past, players swung heavy hickory bats, but the shift to lighter ash bats in the 1920s-40s was groundbreaking. Subsequently, the industry remained relatively stagnant for a while,” he explained. “Innovation arises when individuals ask the right questions and embrace forward-thinking approaches.”
He found it gratifying to witness the enthusiastic response on social media following Saturday’s game. Although some players adopted these bats last season, interest surged during the offseason.
“That’s why you see many players using them now,” Leanhardt mentioned. “The spotlight on them intensified after our recent performance.”
The transition from designing to manufacturing these bats required coordination. Leanhardt claimed to have established rapport with MLB officials overseeing bat regulations and personnel from all major bat manufacturers.
“I’m on a first-name basis with key individuals at MLB who oversee bat compliance and with every bat manufacturer’s lathe operator in baseball,” he shared. “Collaborating with each company and convincing them that producing these bats would benefit their players was crucial. Some embraced the idea, leading to its widespread adoption.”
(Top photo of Aaron Leanhardt, right, with Marlins manager Clayton McCullough: Jasen Vinlove / Miami Marlins / Getty Images)
