MLB 2025: How Red Sox built MLB's best prospect trio - ESPN

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: