The opening weekend of the 2025 MLB season was taken over by a surprise star — torpedo bats.

The bowling pin-shaped bats became the talk of the sport after the Yankees’ home run onslaught on the first Saturday of the season put it in the spotlight and the buzz hasn’t slowed since.

What exactly is a torpedo bat? How does it help hitters? And how is it legal? Let’s dig in.

Read: An MIT-educated professor, the Yankees and the bat that could be changing baseball

What is a torpedo bat and why is it different from a traditional MLB bat?

The idea of the torpedo bat is to take a size format — say, 34 inches and 32 ounces — and distribute the wood in a different geometric shape than the traditional form to ensure the fattest part of the bat is located where the player makes the most contact. Standard bats taper toward an end cap that is as thick diametrically as the sweet spot of the barrel. The torpedo bat moves some of the mass on the end of the bat about 6 to 7 inches lower, giving it a bowling-pin shape, with a much thinner end.

How does it help hitters?

The benefits for those who like swinging with it — and not everyone who has swung it likes it — are two-fold. Both are rooted in logic and physics. The first is that distributing more mass to the area of most frequent contact aligns with players’ swing patterns and provides greater impact when bat strikes ball. Players are perpetually seeking ways to barrel more balls, and while swings that connect on the end of the bat and toward the handle probably will have worse performance than with a traditional bat, that’s a tradeoff they’re willing to make for the additional slug. And as hitters know, slug is what pays.

The second benefit, in theory, is increased bat speed. Imagine a sledgehammer and a broomstick that both weigh 32 ounces. The sledgehammer’s weight is almost all at the end, whereas the broomstick’s is distributed evenly. Which is easier to swing fast? The broomstick, of course, because shape of the sledgehammer takes more strength and effort to move. By shedding some of the weight off the end of the torpedo bat and moving it toward the middle, hitters have found it swings very similarly to a traditional model but with slightly faster bat velocity.

Why did it become such a big story so early in the 2025 MLB season?

Because the New York Yankees hit nine home runs in a game Saturday and Michael Kay, their play-by-play announcer, pointed out that some of them came from hitters using a new bat shape. The fascination was immediate. While baseball, as an industry, has implemented forward-thinking rules in recent seasons, the modification to something so fundamental and known as the shape of a bat registered as bizarre. The initial response from many who saw it: How is this legal?

OK. How is this legal?

Major League Baseball’s bat regulations are relatively permissive. Currently, the rules allow for a maximum barrel diameter of 2.61 inches, a maximum length of 42 inches and a smooth and round shape. The lack of restrictions allows MLB’s authorized bat manufacturers to toy with bat geometry and for the results to still fall within the regulations.

Who came up with the idea of using them?

The notion of a bowling-pin-style bat has kicked around baseball for years. Some bat manufacturers made smaller versions as training tools. But the version that’s now infiltrating baseball goes back two years when a then-Yankees coach named Aaron Leanhardt started asking hitters how they should counteract the giant leaps in recent years made by pitchers.

When Yankees players responded that bigger barrels would help, Leanhardt — an MIT-educated former Michigan physics professor who left academia to work in the sports industry — recognized that as long as bats stayed within MLB parameters, he could change their geometry to make them a reality. Leanhardt, who left the Yankees to serve as major league field coordinator for the Miami Marlins over the winter, worked with bat manufacturers throughout the 2023 and 2024 seasons to make that a reality.

When did it first appear in MLB games?

It’s unclear specifically when. But Yankees slugger Giancarlo Stanton used a torpedo bat last year and went on a home run-hitting rampage in October that helped send the Yankees to the World Series. New York Mets star Francisco Lindor also used a torpedo-style bat last year and went on to finish second in National League MVP voting.

Who are some of the other notable early users of torpedo bats?

In addition to Stanton and Lindor, Yankees hitters Anthony Volpe, Austin Wells, Jazz Chisholm Jr., Cody Bellinger and Paul Goldschmidt have used torpedoes to great success. Others who have used them in games include Tampa Bay’s Junior Caminero, Minnesota’s Ryan Jeffers and Toronto’s Davis Schneider. And that’s just the beginning. Hundreds more players are expected to test out torpedoes — and perhaps use them in games — in the coming weeks.

How is this different from a corked bat?

Corking bats involves drilling a hole at the end of the bat, filling it in and capping it. The use of altered bats allows players to swing faster because the material with which they replace the wood — whether it’s cork, superballs or another material — is lighter. Any sort of bat adulteration is illegal and, if found, results in suspension.

Could a rule be changed to ban them?

Could it happen? Sure. Leagues and governing bodies have put restrictions on equipment they believe fundamentally altered fairness. Stick curvature is limited in hockey. Full-body swimsuits made of polyurethane and neoprene are banned by World Aquatics. But officials at MLB have acknowledged that the game’s pendulum has swung significantly toward pitching in recent years, and if an offensive revolution comes about because of torpedo bats — and that is far from a guarantee — it could bring about more balance to the game. If that pendulum swings too far, MLB could alter its bat regulations, something it has done multiple times already this century.

So the torpedo bat is here to stay?

Absolutely. Bat manufacturers are cranking them out and shipping them to interested players with great urgency. Just how widely the torpedo bat is adopted is the question that will play out over the rest of the season. But it has piqued the curiosity of nearly every hitter in the big leagues, and just as pitchers toy with new pitches to see if they can marginally improve themselves, hitters will do the same with bats.

Comfort is paramount with a bat, so hitters will test them during batting practice and in cage sessions before unleashing them during the game. As time goes on, players will find specific shapes that are most comfortable to them and best suit their swing during bat-fitting sessions — similar to how golfers seek custom clubs. But make no mistake: This is an almost-overnight alteration of the game, and “traditional or torpedo” is a question every big leaguer going forward will ask himself.

At 1:54 ET on Saturday afternoon, New York Yankees play-by-play man Michael Kay lit the fuse on what will be remembered as either one of the most metamorphic conversations in baseball history or one of its strangest.

During spring training, someone in the organization had mentioned to Kay that the team’s analytics department had counseled players on where pitches tended to strike their bats, and with subsequent buy-in from some of the players, bats had been designed around that information. In the hours before the Yankees’ home game against the Brewers that day, Kay told the YES Network production staff about this, alerting them so they could look for an opportunity to highlight the equipment.

After the Yankees clubbed four homers in the first inning, a camera zoomed in on Jazz Chisholm Jr.‘s bat in the second inning. “You see the shape of Chisholm’s bat…” Kay said on air. “It’s got a big barrel on it,” Paul O’Neill responded, before Kay went on to describe the analysis behind the bat shaped like a torpedo.

Chisholm singled to left field, and after Anthony Volpe worked the count against former teammate Nestor Cortes to a full count, Volpe belted a home run to right field using the same kind of bat. A reporter watching the game texted Kay: Didn’t he hit the meat part of the bat you were talking about — just inside where the label normally is?

Yep, Kay responded. Within an hour of Kay’s commentary, the video of Chisholm’s bat and Kay’s exchange with O’Neill was posted on multiple platforms of social media, amplified over and over. What happened over the next 48 hours was what you get when you mix the power of social media and the desperation of a generation of beleaguered hitters. Batting averages are at a historic low, strikeout rates at a historic high, and on a sunny spring day in the Bronx, here were the Yankees blasting baseballs into the seats with what seemed to be a strangely shaped magic bat.

An oasis of offense had formed on the horizon, and hitters — from big leaguers to Little Leaguers, including at least one member of Congress — paddled toward it furiously. Acres of trees will be felled and shaped to feed the thirst for this new style of bats. Last weekend, one bat salesman asked his boss, “What the heck have we done?”

Jared Smith, CEO of bat-maker Victus, said, “I’ve been making bats for 15, 16 years. … This is the most talked-about thing in the industry since I started. And I hope we can make better-performing bats that work for players.”

According to Bobby Hillerich, the vice president of production at Hillerich & Bradsby, his company — which is based in Louisville, Kentucky, and makes Louisville Slugger bats — had produced 20 versions of the torpedo bat as of this past Saturday, and in less than a week, that number has tripled as players and teams continually call in their orders.

WASHINGTON — Arizona second basemen Ketel Marte was put on the 10-day injured list Saturday, a day after leaving the Diamondbacks’ 6-4 victory over the Nationals in the first inning with a strained left hamstring sustained while running the bases.

Marte hit a long ball to the wall in center field, and as he rounded first base and headed to second, he started to stutter-step. He pulled in slowly for a standup double while holding his left hamstring.

“To see him pull up like that in the first inning was not, no one in the dugout was feeling good,” said right fielder Corbin Carroll, who hit two home runs and drove in three runs for Arizona.

Marte limped off the field under the supervision of the team’s training staff and was replaced by Garrett Hampson.

Infielder Tim Tawa was recalled Saturday from Triple-A Reno.

“We budget for these hard times,” manager Torey Lovullo said. “The timing of it isn’t ideal, but we have players that are ready to step in and hold down the fort until he gets back.”

Marte also had hamstring injuries in 2019, 2021 and 2022.

He agreed to a contract Wednesday that guarantees the All-Star $116.5 million through 2031, a six-year deal that includes a player option and $46 million in deferred money payable through 2040.

Marte is hitting .346 this season in eight games and has reached base in every game.

He finished third in National League MVP voting last season, hitting .292 while setting career highs with 36 homers and 95 RBIs.