EARLY IN THE 2023 season, Aaron Leanhardt started asking New York Yankees hitters what they needed to perform better. He was a minor league hitting coordinator for the team, and with league-wide batting average the previous year at its lowest point in more than a half-century, Leanhardt approached that spring with a specific question: How, in an era ruled by pitching, could offense keep up?

“Players were frustrated by the fact that pitching had gotten so good,” Leanhardt said.

An MIT-educated physics professor at the University of Michigan for seven years, Leanhardt left academia for athletics specifically to solve these sorts of problems. And as he spoke with more players, the framework of a solution began to reveal itself. With strikeouts at an all-time high, hitters wanted to counter that by making more contact. And the easiest way to do so, Leanhardt surmised, was to increase the size of the barrel on their bat.

Elongating the barrel — the fat part of the bat that generates the hardest and most contact — sounded great in theory. Doing so in practice, though, would increase the weight of the bat and slow down swing speed, negating the gains a larger sweet spot would provide.

Leanhardt started to consider the problem in a different way. Imagine, he told players, every bat has a wood budget — a specific amount of weight (usually 31 or 32 ounces) to be distributed over a specific length. How could they invest a disproportionate amount of that budget on the barrel without throwing off the remainder of the implement?

The answer led to what could be the most consequential development in bat technology since a generation ago when players forsook ash bats for maple. The creation of the bowling pin bat (also known as the torpedo bat) optimizes the most important tool in baseball by redistributing weight from the end of the bat toward the area 6 to 7 inches below its tip, where major league players typically strike the ball. Doing so takes an apparatus that for generations has looked the same and gives it a fun-house-mirror makeover, with the fat part of the bat more toward the handle and the end tapering toward a smaller diameter, like a bowling pin.

The bat had its big debut over the weekend, as the Yankees tied a major league record with 15 home runs over their first three games. Nine of those came from five Yankees who adopted the bowling pin style: Jazz Chisholm Jr. (three), Anthony Volpe (two), Austin Wells (two), Cody Bellinger (one) and Paul Goldschmidt (one). The hullaballoo over the bats started almost immediately after Yankees announcer Michael Kay noted their shape on the broadcast, and by the end of the weekend players around the league were inquiring to bat manufacturers about getting their hands on one.

The Yankees’ barrage of long balls permeated beyond players’ fascination and into the zeitgeist. Some fans and even opposing players wailed fruitlessly about the legality of the bats — Brewers reliever Trevor Megill called the bats “like something used in slow-pitch softball” after watching his teammates surrender home run after home run over the weekend. But the bats abide by Major League Baseball’s collectively bargained bat specifications for shape (round and smooth), barrel size (no larger than 2.61 inches in diameter) and length (a maximum of 42 inches). Most also didn’t realize that the bowling pin bat was used for some of the most consequential hits of 2024 thanks to one of its earliest adaptors.

Yankees slugger Giancarlo Stanton is owed as much credit as any player for the bowling pin revolution. Leanhardt’s logic behind the bat’s geometry made sense to Stanton, whose average bat velocity of 81.2 mph last year was nearly 3 mph ahead of the second-fastest swinger and more than 9 mph quicker than the average MLB swing. Even with outlier metrics, Stanton gladly embraced a bat that could make his dangerous swing even better — and used it while pummeling seven home runs in 14 postseason games.

TO UNDERSTAND HOW the bowling pin bat works is a lesson in physics. Take a sledgehammer and a broom handle. The sledgehammer will be more difficult to swing because much of its weight is distributed to the tip. The broom handle, meanwhile, can be swung with immense speed but doesn’t contain significant mass. If the length and weight of bats are constants, the distribution of mass is the variable — and Leanhardt conceived of a bat that optimizes both so it can do the most damage.

“This bat is just trying to say: What if we put the mass where the ball is going to hit so that we have an optimized equation of mass and velocity?” said Scott Drake, the president of PFS-TECO, a Wisconsin-based wood products laboratory that inspects all MLB bats to ensure they’re within the regulations. “You’re trying to take a sweet spot and put more mass with that.

“Wood is highly variable,” he added, “and everything is a trade-off.”

In the case of the bowling pin bat, it’s a trade-off hitters using it are willing to make. Because so much of the mass is in the barrel, swings that don’t connect on it produce results often more feeble than those of traditionally tapered models. As Leanhardt said, though, if a ball off the end of a bowling pin shape leaves the bat with an exit velocity of 70 mph compared to 71 mph for the traditional one, both are likely to result in outs. The difference between a 101 mph batted ball and 102 can be a flyout versus a home run.

“That’s the question of the whole wood budget,” said Leanhardt, who left the Yankees after serving as a major league analyst during the 2024 season and currently is the major league field coordinator for the Miami Marlins. “Every penny counts. The fact of the matter is you want your barrels to count the most. You want the most bang for your buck there.”

Turning those principles into reality took buy-in from the entire bat supply chain. Once players bought into Leanhardt’s seedling of an idea, they requested samples from bat manufacturers. Leanhardt worked with a number of MLB’s 41 approved bat makers to make the idea real, and the spec bats were given model numbers that start with BP for bowling pin, though he admits that “torpedo sounds kind of cooler.”

Figuring out the right balance took time. Bowling pin bats take precision to produce. Every fraction of an ounce in bat manufacturing matters. Bats are measured not only on a standard scale but via pendulum-swing tests. The more balanced a bat, the more it oscillates. Traditional bats, their weight distributed disproportionately toward the end, didn’t go back and forth nearly as much.

With relatively lenient regulations from the league allowing manufacturers leeway to create products as long as they stay within the regulations, the new — and perhaps better — mousetrap was born. Stanton’s success was the ultimate proof of concept, and manufacturers came to spring training this year with bowling pin models for players to try in games.

“There’s new pitches getting invented every year,” said Minnesota Twins catcher Ryan Jeffers, who used a bowling pin model in the first three games this year and went 1-for-8. “We’re just swinging the same broomstick we’ve swung for the last 100 years.”

Well, similar at least. Playing in an era when the average fastball velocity was an estimated 10 mph slower than the current average of around 95 mph, Babe Ruth swung a 36-inch, 44-ounce bat. As pitch velocity increased in the decades since, players shaved ounces off bats — tools to ensure they had the requisite speed to catch up with pitches.

“The bat is such a unique tool,” Jeffers said. “You look at the history of the game, and they used to swing telephone poles. Now you try to optimize it, and it feels like some branches are starting to fall for us on the hitting side of things.”

Jeffers, who has spent countless time searching for ways to counterbalance the technological revolution that helped create a generation of pitchers with the best stuff ever seen, swung a bowling pin model from manufacturer B45 in batting practice one day this spring and proceeded to order a batch that arrived during the final two weeks of spring training. Around the same time, Chisholm received his new bowling pin bats and was struck by how he couldn’t tell the difference from his traditional model.

“I mean, it still felt like my bat,” Chisholm told reporters Sunday, echoing Jeffers’ sentiment that bowling pin varieties swing similarly to their standard counterparts. “I hit the ball at the barrel, feel comfortable in the box. I don’t know what else to tell you. I don’t know the science of it, I’m just playing baseball.”

The science is multifold. Beyond the potential increases in exit velocity from the increased mass in the barrel, the weight distribution toward the knob should promote faster swings. Among the five Yankees who have used the bat, all have seen bat-velocity increases year over year, with Volpe up more than 3 mph, Bellinger up 2.5, Wells 2, Chisholm 1.1 and Goldschmidt — an inveterate tinkerer who has also used bats with hockey-puck-shaped knobs — 0.3 mph.

“Credit to any of the players who were willing to listen to me, because it’s crazy,” Leanhardt said. “Listening to me describe it is sometimes even crazier. It’s a long-running project, and I’m happy for the guys that bought into it.”

Because the data — on bat velocity as well as effectiveness — is of such a limited sample, nobody is yet proclaiming that the bowling pin bat will unquestionably revolutionize the game. But more bowling pins will be showing up in major league games soon. Leanhardt said his new team, the Marlins, will feature players using the bat in games. Tampa Bay Rays third baseman Junior Caminero laced an RBI single Sunday with a bowling pin model. In addition to the Yankees and Marlins, the Chicago Cubs and Baltimore Orioles are seen throughout the industry as the teams that have invested the most time and money researching bat geometry and optimization.

One player who does not plan on using the bowling pin model said multiple teammates plan to at least try one in batting practice after the Yankees’ nine-homer outburst Saturday. How many eventually adopt it as their full-time piece depends on feel as much as success. Comfort with a bat is vital for it to go from BP to a big league game, and in a sport where advantages don’t stay secret very long, New York’s might wind up lasting all of one weekend.

“There’s going to be a lot more teams wanting to swing them,” Jeffers said, “because of what the Yankees did this weekend.”