KANSAS CITY -- John McMillon began the year in Single-A Columbia as a 25-year-old reliever looking to get on track.

On Wednesday, he was in the big leagues.

McMillon jumped from Double-A Northwest Arkansas to Kansas City when the Royals’ promoted their No. 25 prospect (per MLB Pipeline) on Wednesday afternoon. In corresponding moves, Kansas City optioned reliever Nick Wittgren to Triple-A Omaha and transferred Brad Keller (right shoulder impingement) to the 60-day IL.

In a span of three months, McMillon pitched at three different levels. He’s still awaiting his big league debut after the Royals’ 6-5 loss to the Mariners on Wednesday at Kauffman Stadium.

It’s been a whirlwind 24 hours for the McMillon family. A day earlier, Double-A manager Tommy Shields told McMillon he had a trip to make, and McMillon’s eyebrows shot up. When he realized that trip was to Kansas City and not simply the bump up to Triple-A Omaha, McMillon was ecstatic. He texted his mom, Laura, to see if she had a minute to talk.

When Laura said she did and John didn’t answer for three minutes, she started to worry.

“You never know what those texts mean,” Laura said from a Kauffman Stadium suite the Royals had set up for the McMillon family on Wednesday.

She sent a follow-up text in all caps: "JOHN."

“And he texted, ‘Hang on Mom, I’m calling you in a minute. It’s a good day,’” Laura said. “That’s when I knew.”

McMillon signed with the Royals as an undrafted free agent after the pandemic-shortened five-round 2020 Draft, making him the first player from that class to make it to Kansas City. The right-hander was drafted twice before -- by the Rays in the 21st round of the 2016 Draft out of Jasper (Texas) High School and by the Tigers in the 11th round of the 2019 Draft out of Texas Tech.

He was originally a catcher at Texas Tech and hit until his junior year, but everything changed when coaches took notice of his arm behind the plate.

“I threw my first bullpen and the pitching coach at the time told me ‘I don’t think this kid will ever pitch here,’” McMillon said Wednesday in the Royals’ dugout at Kauffman Stadium. “They just wanted me to hit, but catching is what developed my arm, no doubt. Making those throws to second. That’s been a big takeaway from my pitching game, just practicing those throws.”

McMillon has a 75-grade fastball, but said he began working on his breaking pitches by throwing wiffle balls in the backyard before translating what worked over to a baseball. His big arm is what made him so sought after in 2020 when teams could sign players for $20,000 after the Draft concluded.

“Sometimes you just get dealt that hand and you have to find out what you want to do,” McMillon said. “... At the end of the day, I feel like the game is going to dictate what happens. I'm encouraged that I'm still sitting here.”

McMillon’s first full professional season in 2021 ended with an injury and just 17 innings under his belt. In 2022, he struggled to throw strikes, walking batters at a 26% clip in Single-A Columbia. He pitched better in Spring Training this year, but the Royals were still unsure where to send him.

He still possessed nasty stuff, including an upper-90s fastball that can touch triple digits, so he went back to Columbia.

“I went out to the field after everybody was told where they were going, and [McMillon is] standing there with a look on his face like he’s going to kill me,” Royals senior director of pitching Paul Gibson said earlier this month. “I said, ‘Are you upset?’ He said, ‘Yeah, I’m upset.’ I said, ‘Good. Go take care of business and everything is going to work out.’

“Well, he pitched with anger and a chip on his shoulder. And we moved him. And we moved him again.”

McMillon started the season with a vengeance. His walk rate dropped to 14% in Columbia to start the year, while he struck out nearly half (48.8%) of the batters he faced and posted a 3.38 ERA across nine appearances (10 2/3 innings). At the end of May, the Royals moved him up to High-A Quad Cities and he got better, with a 2.70 ERA across 13 appearances (20 innings), a 51.9% strikeout rate and 10.4% walk rate.

“I definitely noticed some jumps I had this past offseason with some things I was doing with the pitching department,” McMillon said. “Some of the camps we had last offseason have not only been beneficial for me, but for some other guys we have in the organization. Some of the steps they are taking to make sure we are getting all the information and the data to get better has been something they’re doing here.”

On June 20, McMillon earned the promotion to Double-A. And he got better. McMillon had a 0.87 ERA across 15 appearances (20 2/3 innings) while closing games for the Naturals. He struck out 30 and walked 11.

With the Royals fully committing to getting as many looks at their young players for the future, they decided to have McMillon bypass Triple-A. Kansas City’s bullpen has struggled this year, especially after the Trade Deadline, with a 6.39 ERA since Aug. 1.

Adding McMillon’s power arm may help change that.

“He’s got closer stuff,” Gibson said. “Labeling a closer when a guy is in Double-A is really hard because they have to grow into it. But he’s got closer stuff, closer mentality. Now let’s just see how he evolves.”

For now, McMillon is soaking up the moment. He had several friends and family members in town on Wednesday, including his mom and two brothers, Charlie and Henry.

“John has worked so hard to get here,” Laura said. “He’s such a disciplined person. He takes care of himself, and he’s committed, laser focused. And he’s always been like that. So I know he’s going to go out there and do a great job.”