Veteran reliever Kelvin Herrera, who signed with the Royals as an international free agent when he was a teenager and was a key contributor in Kansas City's 2015 World Series title run, has retired. On Friday, Herrera broke the news on social media with a statement that started with, “Thank you, baseball.”

Hererra, still just 31 years old, made his MLB debut for Kansas City at age 21 in 2011, and from '12-18, the hard-throwing right-hander was one of the best setup men -- and eventual closers -- in the game. In '14, he posted a 1.41 ERA in 70 games for the Royals, following that up with a 2.71 ERA in 72 games the following year, earning the first of two All-Star selections.

“What a reputation he has around here for how he went about his business, the pro that he was,” Royals manager Mike Matheny said Saturday. “What a compliment, what a legacy, in my mind, that when you walk out of this game that you’ve been able to stick around [in], one, have some great experiences, but people are talking about you like he’s been talked about. That’s an indicator of time well spent in the uniform.”

Herrera combined with Wade Davis and Greg Holland -- both in Royals camp this Spring Training -- to comprise the dominant “HDH” trio that helped carry the Royals to back-to-back World Series appearances. Ryan Madson joined the fold in 2015, and Kansas City won its first World Series title in 30 years.

Earlier this spring, Davis and Holland talked about how they still keep in touch with Herrera and reminisce about their memories from those Royals teams.

“I think that’s the greatest part of this game is the connections you make with people from all different walks of life, and Kelvin’s way up there for me,” Holland said. “We grinded it out. He pitched in some really huge spots on short rest or no rest, and you respect that. But you also respect the type of person he is.

“He’s a great friend of mine and he’s not the only one I keep in touch with. I’m kind of a hermit crab, but he’s one of those special guys I talk to a few times in the offseason and try to keep in touch with.”

Herrera was overpowering in the postseason. He’s the Royals’ postseason career leader in appearances (22) and strikeouts (38, tied with Davis) and ranks third in ERA (1.26).

He did not allow an earned run in three appearances for the Royals during their World Series triumph against the Mets in 2015. For many, the memories that stand out most from Game 5 of the '15 World Series are Eric Hosmer’s dash home, Christian Colon’s go-ahead single and Davis’ strikeout that clinched the Series.

But it was Herrera who pitched three scoreless innings in the seventh, eighth and ninth, allowing the Royals to rally, forcing extra innings.

“We’ve been nothing but impressed with every one of the guys who were a part of that championship team, especially that bullpen -- that iconic bullpen," Matheny said. “It was just interesting to watch the progression. You got a seventh, eighth, ninth inning that kind of changed baseball, trying to turn it into a six-inning game and close the door. Everyone after that is trying to look for that same kind of model, and then you see each of them turn into exceptional closers too.”

Overall, Herrera had a 23-27 record over eight seasons with Kansas City, posting a 2.75 ERA and 438 strikeouts in 441 1/3 innings. As the Royals fell out of contention in '18, he was dealt to the Nationals, for whom he had a 4.34 ERA in 21 appearances down the stretch.

Herrera then signed as a free agent with the White Sox, but struggled with Chicago from 2019-20, pitching to a 6.54 ERA in 59 appearances before being released last Aug. 2. He signed with the crosstown Cubs, but he did not appear in a Major League game for them and was released Aug. 26.

Herrera closes his 10-year Major League career with a 3.21 ERA, 1.20 WHIP and 510 strikeouts in 513 2/3 innings.