SEATTLE — Not long ago, tucked inside Busch Stadium in St. Louis, Matt Holliday and John Mabry would sit for long stretches in the batting cages, talking shop.

Around them ran a few young kids with the last names Holliday and Mabry, and as the adults — then a player and a hitting coach for the Cardinals — pondered the difficulties of hitting in the major leagues, the boys played with the carefree nature of youth.

Among them was Jackson Holliday, who is now a 21-year-old rising star for the Orioles. When Mabry first began coaching Matt Holliday, Jackson Holliday was all of 9 years old. Instruction was minimal at that age. His dad really only wanted Jackson to have fun.

“At that point, mostly just pitching to them and letting them be kids,” Matt Holliday said of those hitting sessions with Ethan and Jackson Holliday, as well as JT Mabry. They’d swing without the pressure that is added by large contracts and stadiums full of fans. They’d make a major league batting cage their own playpen.

“I definitely remember him being in the cage and throwing to me and Ethan,” said Jackson Holliday.

A decade after Mabry and Matt Holliday bounced hitting concepts off each other as they talked over the commotion of boys enjoying baseball, Mabry will have a larger role in coaching another Holliday. He joined Baltimore last week as a senior adviser to interim manager Tony Mansolino.

The role is purposely vague. Mabry, a longtime player and coach, will add instruction in multiple areas, including hitting and infield and outfield work. He brings with him the experience of 14 major league seasons as a player, plus hitting coach roles with the Cardinals, Kansas City Royals and Miami Marlins.

Along the way, Mabry has met multiple players he will now work closely with in Baltimore. Ryan O’Hearn, for instance, grew tight with Mabry while they were in Kansas City. But he knows none as well as Holliday, perhaps, because Mabry watched Holliday grow up before his eyes.

“He played with my kid in the family room [at Busch Stadium] for years,” Mabry said. “Small community in baseball, so it’s really cool to have familiarity with those guys and have something to build with.”

It won’t be long until Jackson, like his dad, sits in the batting cage for hours to talk shop with Mabry.

“From what my dad talked about, he’s pretty straightforward, basic approach,” Jackson Holliday said. “I’m excited to pick his brain a little bit. O’Hearn had him a little bit ago and he spoke very highly of him — more recently than me being 12 years old knowing him. So, yeah, I’m excited.”

Matt Holliday first overlapped with Mabry in 2007, when they briefly played for the Colorado Rockies together. It was the end of Mabry’s playing career, and he only appeared in 28 games that season. But even in that limited time, Holliday knew Mabry to be “very kind.”

“His wife and kids, ever since we’ve met them, they’ve been friends of ours,” Holliday said. “Just really, really kind people. I’ve been a big fan of John ever since then.”

Jackson Holliday was a little older than a toddler during that 2007 season, but when Matt Holliday and Mabry reunited in St. Louis, the whole family connection grew. JT Mabry and Jackson Holliday played baseball together on the field or in the cage. And one of Mabry’s daughters attends Oklahoma State in Stillwater, where the Holliday family lives. They’ve stayed in touch through the kids.

Neither Jackson nor Matt Holliday had any idea that Mabry was going to join the Orioles last week, though, until they read it on MLB Trade Rumors. Matt Holliday texted Mabry, “Orioles?” Sure enough, it was true.

Matt Holliday is excited that his son has another well-respected coach in the building to help with his early career development. He remembers combing through “small details” with Mabry when he was a player. Matt Holliday knows that on top of the longer-serving members of Baltimore’s coaching staff, Mabry will add a thoughtful perspective.

“We had a lot of great conversations in the cage. He’s a cage guy like me. We would just sit and talk hitting and bounce some things off each other,” Holliday said of his time with Mabry.

Jackson Holliday hasn’t had much chance to experience the same thing yet, because Mabry’s first day in the dugout was Sunday. Then the team flew across the country, enjoyed an off day Monday and returned to the park for Tuesday’s series opener. But from his memories of old, Holliday remembers Mabry as a quintessential “baseball guy.”

And during Holliday’s draft preparation, before the Orioles selected him with the first pick in 2022, Holliday visited several complexes during a spring break trip to Arizona. One of them was Kansas City’s, and because Mabry was the hitting coach, he talked with Holliday — not as the son of one of his players, but as a soon-to-be professional himself.

“He’s been around a lot of really great players,” Holliday said. “It’s pretty exciting to have a guy like that around.”

If the addition of Mabry leads to anything like what Matt Holliday experienced with Mabry as a coach, it will be a good thing for the club, not only his son.

“I think he brings a really positive attitude, a positive vibe, if you will. He likes to have fun, a good sense of humor, and obviously, if you play that long and you’re a role player for much of your career, part of that niche of being a bench player is having fun and keeping the guys loose,” he said. “He’s old school. He likes to have practical jokes and fun and he didn’t grow up on video games. He grew up on playing cards in the clubhouse and messing with each other. I think it’ll be a fun dynamic to add.”