Editor’s note: This story originally ran on Feb. 26, 2025. Kristian Campbell signed a $60 million extension with the Red Sox on April, 5, 2025.

FORT MYERS, Fla. — Inside the batting cages at the Boston Red Sox‘s spring training complex, where the future of hitting is playing out in real time, the best trio of position prospects in a generation blossomed.

Kristian Campbell, Roman Anthony and Marcelo Mayer have spent hundreds of hours in the building, rotating around its 10 tunnels, though their best work always seems to happen in Cage 4, right inside the main entrance. When they walk through the door, underneath a sign with a Ted Williams quote in big, capital letters — “WE’RE GOING TO LEARN HOW TO DO TWO THINGS … WE’RE GOING TO HIT IT HARD AND WE’RE GOING TO HIT IT IN THE AIR” — they enter a hitting laboratory. Every cage is equipped with a HitTrax that gives them real-time batted-ball data. Trash cans house an array of training bats — overweight and underweight, long and short, skinny. A Trajekt robot, capable of replicating every pitch thrown in the major leagues over the past half-decade, is joined by a dozen other standard pitching machines. Exit velocity leaderboards dot the walls.

Here, Campbell, Anthony and Mayer are in the middle of everything, appropriate for what their future holds. They’re learning modern hitting philosophy, applying it in an array of competitions that aim to turn their tools into skills, jamming to Bachata and Reggaeton and rap and rock, talking immense amounts of trash. On a small desk inside Cage 4 sit two binders outlining the Red Sox’s hitting philosophy: one in English and one in Spanish. These binders outline what the organization’s hitting coaches refer to as its Core Four tenets: swing decisions, bat speed, bat-to-ball skill and ball flight.

As pitchers have leveraged baseball’s sabermetric revolution into designer offerings and a sportwide velocity jump, hitting has fallen behind. Batting average and weighted on-base average (a metric that measures productivity at the plate) are at low points over the past half-century. Pitchers regularly flummox hitters. The Red Sox believe they can bridge the gap. And the new big three — a nickname that was originally given to Mayer, Anthony and Kyle Teel, the catching prospect at the heart of the trade that brought ace Garrett Crochet to Boston over the winter — are the philosophy’s beta test.

“The training environment is the biggest thing with us,” said Anthony, a 20-year-old outfielder. “We push each other so much, and it’s always that competitive — friendly, but competitive — environment we set in the cage. We talk crap to each other. We really try to get the best out of each other and really beat each other in training. And I think it makes us better when we take the field.”

There, their results are undeniable. Mayer, 22, is a smooth-fielding, left-handed-hitting shortstop who fell to the Red Sox with the No. 4 pick in the 2021 draft, weathered injuries and saw his exit velocity spike and strikeout rate dip last year. Anthony, who signed for a well-over-slot $2.5 million bonus after Boston chose him with the 79^th pick in the 2022 draft, is widely regarded as the best hitting prospect in the minor leagues. The 22-year-old Campbell, a fourth-round pick in 2023 as a draft-eligible redshirt freshman, was a revelation last season, the consensus Minor League Player of the Year who went from unheralded to a prospect coveted even more than Anthony by some teams despite an unorthodox swing.

All three will be in the major leagues sooner than later — for Campbell, perhaps by Opening Day. They’ll bring with them a shared experience they believe will transfer to the big leagues. When they eventually face Yankees ace Gerrit Cole, they’ll have a sense of what to expect, not just because they stood in against him on the Trajekt but because coaches took his best fastballs (100 mph at the top of the zone), added an extra half-foot of rise to them and challenged the kids to hit it.

“You want to be surrounded with the best,” Anthony said, “because it makes you want to become the best.”

IN SEPTEMBER 2023, after the minor league season ended, the Red Sox gathered their minor league prospects at their spring training complex for a two-month offseason camp. Boston’s staff assesses every hitter to form an action plan, and Campbell’s was clear. He made excellent swing decisions and had elite bat-to-ball ability, both of which manifested themselves as he hit .376 with 29 walks and 17 strikeouts over 217 plate appearances in his lone season at Georgia Tech. While the 6-foot-3, 210-pound Campbell swung the bat hard, the Red Sox saw room for improvement. Ball flight represented the biggest area of need after his average launch angle during 22 postdraft pro games was just 2 degrees.

Inside the complex’s cafeteria one day in camp, Campbell was surveying his options when Red Sox hitting coordinator John Soteropulos meandered by. Soteropulos had joined the team after three years as a hitting coach at Driveline Baseball, the Seattle-based think tank where philosophies have pervaded the game over the past decade. Soteropulos noticed shepherd’s pie on the cafeteria’s menu and alerted Campbell.

“You need to eat that,” Soteropulos said. “It’s got bat speed in it.”

“I hope it has ball flight, too,” Campbell said.

While Mayer entered the MLB ecosystem as a top prospect and Anthony a tooled-up could-be star, Campbell was different. Taken with the compensatory pick the Red Sox received when longtime shortstop Xander Bogaerts signed with the San Diego Padres, Campbell signed for less than $500,000. His swing was janky. He needed work. Soteropulos, director of hitting and fellow Driveline alum Jason Ochart and assistant farm director Chris Stasio were empowered by Red Sox management to implement their new systems in hopes of extracting the best version of later-round picks like Campbell — and if it worked, he would represent the proof of concept.

From the moment he arrived in the organization, Campbell impressed the staff with his desire to learn. And challenging players beyond the perfunctory repetitions hitters take — the same soft flips in the batting cage, the same 60 mph batting practice before every game — is at the heart of Boston’s philosophy.

Professional baseball players, the thinking goes, are elite problem solvers. Giving them complex problems drives them to adapt. If they train in environments that don’t take them outside of their comfort zone, improvement is negligible. Challenging hitters, whether with the Trajekt or with machine balls that fly only when struck on the sweet spot or with slim bats that emphasize barrel control or hundreds of other ways, forces that adaptation. And it’s those changes that take a nonexistent or atrophied skill and give it heft.

“I really wanted to go to a team that could develop me into a great player and that will take the time to help me because I feel like I’m really coachable and I listen,” Campbell said. “I just need the right information. And if I don’t know what I’m doing, it’s hard for me to correct and change things.”

Over those two months, the Red Sox didn’t overhaul Campbell’s swing as much as they found the best version of it. Thirty years ago, Coop DeRenne, a professor at the University of Hawaii, ran a study on overload and underload training that showed it significantly improved bat speed. The industry has mostly ignored its findings, but Driveline embraced them and brought them to the Red Sox. Campbell trained two days a week with bats that were 20% heavier and 20% lighter than standard 31-ounce bats. Though he whipped his bat through the zone with a preternatural ability to stay on plane — the angle of the bat meeting the angle at which the pitch arrived at home plate — delivering the barrel with greater force reinforced a tenet Red Sox coaches preach repeatedly: “The bats do the work for you.”

The bigger challenge was adulterating Campbell’s swing to hit the ball in the air. Williams, who wanted to be known as the greatest hitter who ever lived, long advocated for ball flight because he understood a hard-hit ground ball is typically a single while balls struck in the air produce the vast majority of extra-base hits. Pulling the ball in the air is particularly important. The longer a bat takes to make contact, the more speed it generates. Meeting a ball in front — which typically allows a hitter to pull — maximizes the capacity for damage.

Rather than overhaul Campbell’s swing, the Red Sox preferred to let his natural athleticism guide him toward a solution. Instead of moving his hand position or getting rid of his toe-tap, Campbell altered where he wanted to strike the ball, reminding himself with every rep to do something counterintuitive: Swing under it.

“For me, it’s just a feeling,” Campbell said. “You got to know where your barrel is at all times. It was in an odd spot because I was trying to get more elevation on the ball than normal. So I feel like I have to swing under the ball to hit it in the air. And I really was on plane because I’ve been so on top of it all these years.”

Campbell’s barrel aptitude improved by taking reps with a fungo bat or a slim 37-inch bat (3 to 4 inches longer than the standard bat), which forced him to meet the ball farther in front of the plate. The skills learned in doing so eventually meld with a hitter’s’ regular bats, and variations of drills — offsetting standard pitching machines to the side, mixed-pitch Trajekt sessions — allow them to be applied in new, challenging environments. In the cages in Ft. Myers, coaches pitted Campbell and his fellow prospects against one another to see who could hit the ball hardest or most consistently. Winners gloated — “Marcelo talks s— 25/8,” Anthony said — and those who didn’t win returned the next day intent on revenge.

When last winter’s offseason sessions ended, the Red Sox were hopeful they would translate into a breakout season for Campbell. Even they could not have predicted what transpired over the ensuing months. Campbell said he came into 2024 hoping to hit five home runs — one more than in his lone college season. He started the season at High-A Greenville and hit his fifth home run May 9. Less than a month later, with three more home runs on the ledger, he ascended to Double-A, where he spent two months and whacked eight more homers. He was promoted to Triple-A for the final month and added another four, finishing the season hitting .330/.439/.558 with 20 home runs, 24 stolen bases, 74 walks and 103 strikeouts in 517 plate appearances.

“I remember the first time I saw him hit, I was like, ‘The hell is this?’ ” Mayer said. “He’s in the cage with the weirdest swing I’ve ever seen, and he’s got his long bat, and I’m like, ‘What?’ Next thing I know, he’s hitting .380.”

When Red Sox shortstop Trevor Story first saw Campbell on a rehabilitation assignment in Triple-A, he was taken by his ability “to self-organize and learn how to solve problems.”

“He has a special talent for moving the bat,” Story said. “His bat speed is just violent. When you hear it, you’re like, oh, s—.”

“It’s controlled violence,” Campbell said. “You got to make sure you see the ball. And then whenever you make a decision to swing, you got to put your fastest, hardest, best swing on it and make sure you stay somewhat under control while that ball is going on so you can hit the ball as well as possible.

“Every swing really can’t be the same. The way pitches move and how good everybody is nowadays, if you take the same swing every time and only can hit certain pitches, that’s a mistake. You’ve got to be able to adjust to different things, different pitches, different locations.”

DURING THE FIRST week of this year’s spring training, before the full Boston squad reported, Red Sox Hall of Famer Dwight Evans stood outside of Cage 4 and admired what he was seeing. Evans spent two seasons as a hitting coach, in 1994 with Colorado and 2002 with the Red Sox, and he recognizes baseball’s evolution. The game changes, and even if all the technology isn’t his cup of tea, he isn’t going to argue with the results.

In Campbell, Mayer and Anthony, he doesn’t see prospects. Without an at-bat to their names in MLB, they remind Evans — who spent 20 seasons in the major leagues, 19 with Boston — of his peers.

“It’s almost like they’ve been around 10 years in the big leagues,” Evans said. “They just have it. They know what they’re trying to do.”

The Red Sox believe this is just the beginning for Campbell, Mayer and Anthony and that their approach to hitting will create a pipeline of prospects to join a core that includes the trio alongside All-Stars Rafael Devers, Jarren Duran, Alex Bregman and Story, and the young and talented Triston Casas and Ceddanne Rafaela. Buy-in at all levels is paramount, and chief baseball officer Craig Breslow, assistant general manager Paul Toboni and farm director Brian Abraham are leaning into the work done by Ochart, Soteropulos and Stasio. Breslow hired Kyle Boddy, who founded Driveline, as a special adviser. Five other former Driveline employees dot the player development, baseball science and major league staffs, and Stasio was promoted over the winter to director of major league development, a new role in which he will apply the development philosophies to the big league club and maintain the continuity for prospects who ascend to Fenway Park.

Campbell is in line to be the first — of many, the Red Sox hope — to crack the big league roster. He’s in competition for the second-base job this spring, a testament to the organization’s belief in him. If he wins it, Bregman will play third and Devers — who has received MVP votes five of the past six years and signed a franchise-record $313.5 million contract — will move to designated hitter, a role he said unequivocally he doesn’t want to play.

The Red Sox see Campbell as worth the potential drama. Perhaps it’s a function of five playoff-free seasons in six years since their 2018 World Series title, but it’s likely simpler: Campbell is too good to keep down. Mayer and Anthony won’t be far behind. The competition fostered in Cage 4 — and the work ethic it demands — isn’t going anywhere.

Even before Campbell’s arrival, Mayer and Anthony had grown close through late-night, postgame hitting sessions. Both have beautiful left-handed swings, more traditional than Campbell’s in which he waggles the bat, pointing it almost directly toward the sky at the swing’s launch point. Starting from a better place than Campbell hasn’t kept either from reaping the benefits of Boston’s program.

“I don’t know if I’m hitting the ball harder because it’s necessarily bat speed or because I’m working in the gym, but both together could only help,” Mayer said. “So over the years, I feel like I’m hitting it harder, I’m moving the bat quicker. I have a better understanding of my swing. So all those things tie in and play a big role and lead to success.”

Knowing which prospects will find major league success is impossible, though in an era defined by objective data, the misses aren’t nearly as frequent. There was no bat-speed data when Eric Hosmer, Mike Moustakas and Wil Myers were all top-10 prospects for Kansas City in 2010. Trajekt was a dream machine when Arizona had Justin Upton, Chris Young and Carlos Gonzalez in 2007. Exit velocity was the domain of rocket ships in 2004 when Rickie Weeks, Prince Fielder and J.J. Hardy were coming through the Milwaukee system.

It’s a whole new baseball world, and it is on full display in Cage 4, where Campbell, Mayer and Anthony have spent so much time working with their instructors that they joke that Soteropulos might as well sleep there.

“It’s pretty cool to think about how many spring trainings we’ve been in there,” Anthony said. “Looking back at it and being on the big league side, just appreciating guys like John and guys on the minor league side that take so much time out of their days to get us better.”

For all the struggles hitters around baseball have faced, the Red Sox believe in their system — and in this first generation that will serve as a litmus test to its efficacy.

“I’m committed to the game,” Campbell said. “I want to be the best player I can be every day. I want to bring whatever I can to Boston. Once I knew they drafted me, I was like, ‘That’s the team I’m going to debut with. That’s the team I’m going to play with. I want to play with the team for a long time.’ I just knew that I’m going to give all I have to this team that took a chance on me. I’m going to make sure it’s worth it for them and me.”