The best thing that happened to Jackson Holliday in the early chapter of his baseball career was the fact that he was relatively ordinary during his time on the summer showcase circuit before his senior year of high school.

It might sound overdramatic to say a 20-year-old phenom has had a huge turning point already, not to mention one that occurred when he was 17. But Holliday’s pedestrian summer really set things in motion for him to become the No. 1 pick in the 2022 Draft and the top prospect in all of baseball at the time of his highly anticipated big league debut. And it was a sign of some of the attributes that have the Orioles -- and most of baseball -- confident he will manage this final promotion like he has all the others in his young pro career.

• Watch Holliday's debut at 7 p.m. ET: FREE on MLB.TV or on MLB Network

“He just blended in during the summer at the Area Code Games,” said one cross-checker who saw Holliday multiple times that summer and the following spring. “He was just another guy that needed to go to college. Obviously, from the Area Code Games to the spring, he matured and got bigger and stronger. The overall tool set improved considerably -- the run tool increased, the bat speed and the overall raw power tool improved. It’s a testament to the kid and his work ethic.”

• MLB Pipeline | Top 100 prospects | Prospect video

An area scout in Oklahoma had turned him in as a second- or third-rounder following the summer. There were “glimpses of really interesting things,” he said, but also concerns about the swing-and-miss in his game and some drift in his swing that hampered his consistency at the plate. In the spring, he was an entirely different player with some coil to his swing and the ability to stay on his legs, not to mention the added physicality and athleticism also noted by the cross-checker. But it was more what was behind the transformation that stood out, something that continues to make Holliday the elite prospect he is.

“The changes he made in the box for a 17- or 18-year old were amazing, so it’s no surprise to see the success he’s had so far in his pro career,” the area scout said. “You knew he’d get bigger and stronger, but he made changes to his approach and his swing and he stuck with that whole process. He just bought in, took off and never looked back.

“He had the ability to slow things down in the box I’d not seen before. The belief in himself was incredible. He knew how good he was, that he needed to go out and do it. And he did it.”

Scouts will often say that seeing how a player handles adversity is just as telling as watching him hitting home runs or stealing bases. And Holliday clearly took the lumps from that summer, then used it as motivation and a guide to the tireless work he put in to get to the next level as a high school player. The buy-in is the most incredible thing because it hasn’t changed to this day. The son of former Major League All-Star Matt Holliday was confident but not cocky, and he never questioned whether he was on the right path.

• Born for this: Holliday grew up ready for MLB debut

“I believe he believes in the plan for himself,” the area scout said. “For how loud everything came on that spring, and that quick, I never saw him press. He was the same guy, same approach -- that was one of the most impressive things I’ve seen on the amateur side. He was the same kid and you can’t say that about many people. The self-belief never wavered. He didn’t panic, he never got angry. He’s mature beyond his years.”

Talk to anyone who has been around Holliday at all and you’ll get some version of that “mature beyond his years” observation. The fact he skyrocketed up Draft boards didn’t change who he was. The fact he played across four levels of the Minors in his first full season and finished with a .323/.442/.499 line didn’t alter the way he carried himself. He went back home and got back to work to become an even better player, basically living in the baseball gym/barn built at his home in Oklahoma.

• An inside look at No. 1 prospect's incredible workout facility

When he posted a .954 OPS this spring and the world was clamoring for him to make the Opening Day roster, his internal clock stayed the same. He simply went back down to Triple-A Norfolk and slashed .333/.482/.595 over 10 games. He knew the call would come eventually -- and now the moment has arrived.

Rather than project what kind of statistical levels he can reach in his rookie season, it’s better to tell Orioles fans what to expect in terms of what makes Holliday tick. And listening to teammates twho have been with him during his rise up the levels of the farm system talk about what makes Holliday special, it’s clear fans should expect the same kind of even-keeled, quietly confident, never-satisfied player who scouts saw in high school.

“I would say just the way he handles himself as a young player -- doesn’t matter if he is 0-for-4 or 4-for-4, he’s still a threat in the box,” a fellow Orioles prospect said. “I always have the utmost confidence when he’s in the box that he’s going to get on base. Maybe not a hit every time, but he can draw walks and have great at-bats all the time. And he’s taken a huge step with his glove -- he looks like a veteran at second base, he’s so smooth. You would never know he’s 20 years old.”