NEW YORK — The New York Yankees’ bats were the story of the team’s franchise-record nine-home run day against the Milwaukee Brewers on Saturday. Then came the discussion about the actual bats used by some players in the 20-9 win.

The uniquely shaped lumber is the result of two years of research and experimentation with a former Massachusetts Institute of Technology physicist-turned-coach at the helm.

The question at its center?

“Where are you trying to hit the ball?” Aaron Leanhardt said in a phone interview Sunday morning. “Where are you trying to make contact?”

Leanhardt, 48, began his work when he was a member of the Yankees’ minor-league hitting department in 2022 and brought it to the major leagues last season when he was the team’s lead analyst, with some players, including shortstop Anthony Volpe, trying them in games. Now, as many as five Yankees will be using them in games at least early this season, according to outfielder Cody Bellinger.

The bats — with their torpedo-like shape — are custom-made to player preferences and are designed so that the densest part of the bat is where that particular hitter most often makes contact with the baseball, said Leanhardt, who became a field coordinator with the Miami Marlins in the offseason.

“Really,” he said. “It’s just about making the bat as heavy and as fat as possible in the area where you’re trying to do damage on the baseball.”

A Major League Baseball spokesman told The Athletic that the bats don’t break any rules. MLB Rule 3.02 states that a bat “shall be a smooth, round stick not more than 2.61 inches in diameter at the thickest part and not more than 42 inches in length. The bat shall be one piece of solid wood.” It also says that “experimental” bats can’t be used “until the manufacturer has secured approval from Major League Baseball of his design and methods of manufacture.”

Asked whether he was the inventor of the technology, Leanhardt said it was a group effort, the results coming from conversations with coaches, players, MLB and bat makers.

“Credit goes to those who take it,” Leanhardt said. “But if people want to ascribe credit to different people, then I’ll take some cut of it.”

A Yankees official, however, said Leanhardt deserves “a lot” of the credit. Retired infielder Kevin Smith, who spent parts of four seasons in the majors, also credited 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 took an unorthodox route to baseball.

He has a bachelor’s degree in electrical engineering from the University of Michigan and a Ph.D. in physics from MIT. He was a physics professor at the University of Michigan from 2007 to 2014.

Leanhardt began coaching in the Atlantic League in 2017 and coached at a Montana community college before joining the Yankees in 2018. In the majors in 2024, the club said he was its first “major league analyst” and “responsible for integrating the use of quantitative information with on-field performance and preparation.”

Why leave academia for baseball?

“I think that’s one of the cool things about sports is it’s very competitive,” he said. “Guys are willing to push the envelope. It’s just an opportunity to take my background to an area and find ways to innovate.”

Talking to players over the years revealed that their biggest concerns were twofold, Leanhardt said. They wanted to make more contact with pitches and they wanted to strike the ball more often with the bat’s “sweet spot,” or the densest area.

“They’re going to point to a location on the bat that is probably six or seven inches down from the tip of the bat,” he said. “That’s where the sweet spot typically is. It’s just through those conversations where you think to yourself, why don’t we exchange how much wood we’re putting on the tip versus how much we’re putting in the sweet spot? That’s the original concept right there. Just try to take all that excess weight and try to put it where you’re trying to hit the ball and then in exchange try to take the thinner diameter that used to be at the sweet spot and put that on the tip.”

Leanhardt said he didn’t see many drawbacks to redistributing the weight of the bat.

“The bat speed should stay the same,” he said. “Maybe the bat speed can even increase a little bit depending on how you want to redesign the bat. But ultimately you’re getting a fatter barrel, a heavier barrel at the sweet spot. So in some sense, you can have your cake and eat it here too. You can get some gains without actually making sacrifices.”

Leanhardt said he didn’t want to talk about individual players’ experiences with the new bat. Yankees designated hitter Giancarlo Stanton told reporters earlier this month that it was “probably some bat adjustments”  last season that caused the ligament tears in both of his elbows that led to his current stay on the injured list, though he didn’t place specific blame on anybody. Then he added: “I don’t know why it happened.” Leanhardt declined to comment on Stanton’s situation.

“You’d have to ask the Yankees’ medical personnel about that,” he said. “I’ll defer all those questions to the Yankees’ medical guys.”

Leanhardt said it was “the nature of our business” that it took years for a radically new bat design to come along.

“People back in the day swung very heavy bats made out of hickory and then someone had this genius idea to swing something lighter, something like ash, and that was revolutionary back in the 1920s, ’30s, ’40s kind of in that transition, and then the industry kind of stayed the course for quite some time,” he said. “Ultimately, it just takes people asking the right questions and being willing to be forward-thinking.”

He got a kick out of seeing the social media fervor the bats caused Saturday. He said that while some players began to use them last season, “the entire industry kind of caught wind of it” and “it exploded in the offseason.”

“Which is why you see it in the hands of so many guys right now,” he said. “Obviously, (Saturday’s) performance threw a whole lot of attention to it.”

It took a lot of coordination for the bats to go from the design stage to being manufactured. Leanhardt said he would “guarantee” he’s on a first-name basis with officials at MLB who oversee bat regulation and “everyone who operates the lathe for every bat manufacturer in baseball.”

“You really just are communicating with each company and trying to find the person who really knows the wood and knows how to turn the wood on a lathe. You just build a relationship with those guys and convince them that this is something that’s in their best interest to produce for their players. They want their players to be as successful as possible. Some guys buy in and it gains traction,” he said. “That’s really how it got built up.”

(Top photo of Aaron Leanhardt, right, with Marlins manager Clayton McCullough: Jasen Vinlove / Miami Marlins / Getty Images)