KANSAS CITY -- On Friday night at Kauffman Stadium, the Royals featured something that had never happened in baseball.

When Jon Heasley took the mound for his Major League debut in Kansas City’s 6-2 series-opening loss to the Mariners, the 2021 Royals became the first to have five pitchers from the same Draft class to start a game for that team in the same season, according to the Elias Sports Bureau.

Heasley, a 13th-round pick in the 2018 Draft and ranked as the Royals’ No. 14 prospect by MLB Pipeline, made the jump from Double-A Northwest Arkansas to the Majors to start in place of Brady Singer (injured list), who was the 18th overall pick in ‘18. Watching Heasley’s four-inning debut were three other members of that Draft class and the current Major League rotation: Jackson Kowar (33rd overall pick), Daniel Lynch (34th) and Kris Bubic (40th).

And a bonus: Kyle Isbel, the Royals’ third-round pick in 2018, started in right field for Heasley’s debut.

Add 24-year-old starter Carlos Hernández to that group, and the future that is so often talked about in Kansas City is starting to take shape now.

Heasley found out he was making his debut on Thursday morning, when Northwest Arkansas manager Scott Thorman called him to the ballpark early and told him the news.

“Words can’t explain the feeling,” Heasley said. “… They mentioned that if we don’t make the playoffs, I might go make a few starts in Triple-A, but no, this was not really in the thought process. But here we are.”

There Heasley was on Friday with his family watching in the stands. After laughing off the first warmup pitch that sailed to the backstop, Heasley settled in for an 11-pitch, clean first inning.

Heasley allowed four runs on six hits with two strikeouts, no walks and one hit batter. Working with a pitch count like most of the Royals’ young pitchers this late in the season, Heasley needed 75 pitches to work around traffic, and those four runs all came off the bat of Jarred Kelenic.

The Mariners’ young phenom rocketed a pair of two-run homers, the first coming in the second inning on an inner-middle changeup, which Kelenic turned on and deposited in the right-field seats.

The second came in the fourth inning on a curveball on the outside part of the zone. Kelenic crushed it, as the ball traveled a Statcast-projected 435 feet to straightaway center field.

“Getting 3-0 to him both times didn’t help,” Heasley said. “But I didn’t want to walk the guy, so I was trying to attack him, pound the zone. … These are big league hitters now, so they’re not going to miss them when you leave them in the middle.”

Heasley has been lights out in Double-A with a 3.33 ERA across 105 1/3 innings and 22 appearances (21 starts). He’s struck out 120 batters for a 10.3 strikeout-per-nine ratio.

Mastering Double-A is one thing; the big leagues is an entirely different beast. But Heasley navigated a Major League lineup well enough for his debut, learning a few things along the way.

“I think he’s pretty fearless,” manager Mike Matheny said. “I think it’s something you need to experience, being on a Major League field, making some good pitches and having some success. And then learning from some of the ones that didn’t go his way.

“That stuff will play. Those are three above-average pitches.”

Those two pitches to Kelenic ballooned Heasley’s line, but the big right-hander showed some impressive stuff. He kept the Mariners guessing with three pitches, including his fastball that topped out at 97.6 mph -- a few registered as sinkers because of the run it sometimes has. Heasley showed confidence with his signature curveball and a changeup that, when he gets the right speed on it, shows good depth.

“I told him when he got taken out, ‘We can win a lot of games with you doing that,’” Whit Merrifield said.

Heasley didn’t let the moment rattle him, a demeanor that has been apparent since he was drafted and is why the organization was confident in the jump from Double-A to the Majors.

“I’m not surprised, just from what I do know about him and what the organization knows,” Matheny said. “That’s why you would do something like we did. Understand that this guy is going to come out and compete, not going to be overwhelmed.”

Heasley said he felt more confident with that young group of pitchers greeting him in the clubhouse on Thursday and watching from the dugout on Friday. Heasley was the first player Bubic met in the organization after being drafted, and the lefty got to hand Heasley the ball from his first career strikeout.

“That’s where the fun starts,” Merrifield said. “Now you have to figure out how to be successful up here and help us win games. ... Lot of young talent, and glad they’re here.

“Now it’s time to take a step forward.”