KANSAS CITY -- The Royals brought in several relievers this offseason to remake the back end of their bullpen with strike throwers and veterans who can handle the moment.

But the future of that unit still rests heavily on homegrown pieces, and one arrived in Kansas City on Thursday.

The Royals called up reliever and No. 18 prospect Will Klein as the corresponding move for starter Alec Marsh being placed on the injured list. Klein’s first appearance will be his Major League debut. He got the call from Triple-A Omaha manager Mike Jirschele late Wednesday night.

“Are you serious?” Klein asked Jirschele.

“Nah, I’m just kidding,” Jirschele dead-panned.

Klein knows Jirschele’s sarcasm when he hears it, so quickly he began packing up his life in Omaha, ready to hit the road early Thursday morning to get to Kauffman Stadium in time for the afternoon series finale against the Blue Jays. He FaceTimed his wife, Carson, late Wednesday and called his mom, Brittany. His dad, Bill, didn’t answer because of the Do Not Disturb setting on his phone, so Bill woke up to a text Thursday morning. All three are making the trip to Kansas City on Thursday.

“It was cool to be able to share that with my parents, too, because they put in as much work as I did,” Klein said.

Added to the 40-man roster last November in order to protect him from the Rule 5 Draft, the 24-year-old Klein has risen through Kansas City's farm system since he was selected in the fifth round of the abridged 2020 MLB Draft out of Eastern Illinois University.

He’s built his reputation as a future back-end bullpen piece by throwing in the upper-90s, flipping in two nasty breaking balls and showing a cutter that throws hitters off balance.

With Triple-A Omaha this year, Klein has allowed just one unearned run in 11 innings over nine appearances. He’s struck out 12 and walked six, but has been more in the zone recently.

“Throwing more strikes,” Klein said when asked what has gone well to begin the year. “I’m pretty happy with that. I got a little too timid last year in the zone, giving too much credit to the hitters. … I need to attack the zone and make it harder on them to [hit]. Especially getting in my counts, make it really hard on them.”

At 6-foot-5 and 230 pounds, Klein is also an imposing presence on the hill, his fire-red beard only the first sign of the fireball pitcher he becomes when he steps on the mound.

“He’s got big stuff,” manager Matt Quatraro said. “Upper 90s, 100 mph, two good breaking balls. Really the little bit that I got to be around him, it was more about the fearlessness he has to believe he belongs out there. He can be elite. He’s got good pitch characteristics, two breaking balls, with that velo. He needs to be in the zone, but he’s also the kind of guy who can get [opponents to] chase.”

A hard-throwing, upper-90s reliever is something the Royals bullpen lacks this year, although the results have been good without power arms. With Carlos Hernández and Jake Brentz on the injured list, the Royals are relying on strike-throwing and good defense in the late innings of games.

Klein has a chance to emerge as that power arm. The Royals likely won’t throw him into high leverage moments right away, but it wouldn’t be surprising to see him pitch his way into those situations soon enough.

All that matters to Klein, now, though, is pitching the way he knows how and helping the Royals win.

“That call was great, exciting and a dream come true,” Klein said. “But now you get here, you’ve got to go perform and do your job again. I got to take in the moment a little bit this morning, but now it’s just back to baseball.”