SEATTLE — When Jackson Holliday arrived in Triple-A late in 2023, he discovered a problem. He has always been an aggressive hitter — why wait? — but as the Orioles infielder adjusted to life at the highest level of the minors, he discovered that, while he could hit just about everything, he shouldn’t.

The low-and-outside fastball that he could still reach? Sure, he could put that in play, but he couldn’t produce much damage against a pitch like that.

For a moment, Holliday almost swung too far in the other direction. His dad, seven-time All-Star Matt Holliday, said Jackson “got a little bit passive” in the minor leagues. Jackson Holliday wonders now if he just had to wait for better pitches longer down there because “maybe [he was] a little bit more feared in the minors.”

Whatever the case, Jackson Holliday has released the aggression he reined in during previous seasons. Holliday, a breakout star for the Orioles, has proved to be not only an aggressive hitter early in counts but a hitter who makes the most of early swings.

Holliday entered Thursday tied for 14th in baseball for the most first-pitch swings against fastballs. On that list, he’s joined by some of the best hitters in the game, including Rafael Devers, Cal Raleigh, William Contreras, Bryce Harper and former teammate Kyle Stowers.

Overall, Holliday is swinging on the first pitch 42.1% of the time. Those swings have led to positive results. When he makes contact on first-pitch swings, Holliday is hitting .351 — an argument for remaining selectively aggressive.

“When you step into the box, you’ve got to be ready to hit,” said Matt Holliday, who remains an adviser for Jackson Holliday. “Especially nowadays, with the kind of off-speed stuff that these guys are featuring and the strikeout pitches, and just the nature of the game as far as the kind of pitching you’re facing, if you get a good pitch early in the count, you’ve got to be ready to hit it, whether it’s a fastball or it’s a strike breaking ball or a changeup that stays up. Be ready. That’s something he’s always enjoyed doing.”

Jackson Holliday is particularly aggressive when compared to other Orioles. Ryan O’Hearn, the best producer on the team currently, also thrives when swinging at first pitches (a whopping .538 batting average). But Holliday hunts first-pitch fastballs far more than his teammates.

He has taken 27 at-bats in which he has swung at a first-pitch heater. The next closest is O’Hearn, who has done so in 18 at-bats.

“I don’t usually like to take fastballs in the middle, especially if I’m hunting heaters,” Holliday said. “In the middle of the plate, I’m probably going to pull the trigger early on anything kind of close.”

Holliday is confident in his ability to adjust to a hanging breaking ball out of the pitcher’s hand if he’s sitting on a fastball, so early in counts, he’ll let loose.

“If a guy has a lot of heaters and then tries to throw a get-me-over breaking ball,” he said, “I usually can pull the trigger on that because I’m hunting heaters.”

The aggression has helped Holliday flourish, especially as he takes the leadoff role as his own. Traditionally, a leadoff hitter is more likely to work the count. But, in the era of advanced data, those on deck know what’s coming out of the pitcher’s hand. They don’t need to see it against Holliday first to be prepared.

Those behind Holliday, he surmises, are also part of the reason he’s getting so many first-pitch fastballs to attack. With Adley Rutschman and Gunnar Henderson generally following Holliday in the batting order, pitchers aren’t eager to nibble around the strike zone to Holliday, reluctant to issue a walk that would put a runner on base for some of the heavier hitters to drive in.

“You have a lot of guys who can protect me in this lineup behind me, and that’s definitely helpful,” Holliday said. “You get attacked a little bit more.”

Holliday said a base-stealing threat on first base, such as Jorge Mateo, will also give him an opportunity against more fastballs because pitchers don’t want to miss a breaking ball in the dirt — potentially allowing a free 90 feet to a runner.

When Matt Holliday considers his son’s first-pitch tendency, he said, the trickle down of success in those situations can change the way pitchers throw to Jackson Holliday.

“He’s not afraid to get after it. He’s not tentative. At least he hasn’t been this year. I think it’s good,” Matt Holliday said. “It might be the best pitch you get the whole at-bat, and you don’t let guys steal a strike. And now they’re a little more careful and you might get more 1-0 counts, and you might find yourself in better counts because they know you’re coming out firing. They might start throwing more off-speed, or they’re picking a little bit more and throwing a few more balls. So, I think in the long run, it might set him up for better counts, too.”

Still, there are instances when Jackson Holliday knows he was too aggressive. He recalled a first-pitch slider he hit last month against the Boston Red Sox. He was out in front and rolled the pitch over to the first baseman for a groundout.

That’s part of the learning curve the 21-year-old finds himself embracing. But, on the whole, “I’d rather err on the side of aggression,” and he has to good effect.

“That’s kind of my approach most of the time,” Holliday said. “I just happen to be getting a lot of strikes early and I’ve gotten some pitches to hit, and it’s been really helpful for me to be aggressive and try to put the ball in play.”