DETROIT -- The Yankees were in Kansas City last May and had been seeing a parade of hard-throwing young pitchers out of the Royals' bullpen: Tim Collins, Aaron Crow, Louis Coleman, Nate Adcock.
Then, in the seventh inning of the series' third game, in came right-hander Kelvin Herrera. He promptly buzzed a 100-mph fastball past Derek Jeter. As the story goes, a startled Jeter turned to the catcher and the home-plate umpire, shook his head and exclaimed: "Where do they find all these guys?"
Herrera smiled as he heard the story: "He said that?" If Herrera had not heard Jeter's remark, he certainly remembered the pitches he threw. Herrera had the great Yankees captain thinking about that fastball.
"I threw a changeup after that pitch and he missed it," Herrera said, demonstrating a woeful swing. "Then, he hit a ground ball to third."
A weak grounder, off another 86-mph changeup, to Mike Moustakas. It was an early step in the maturation of Herrera as a promising and prominent relief pitcher. Almost every step has been a positive one.
"He's a special-type guy, a special pitcher," Royals pitching coach Dave Eiland said.
There have been setbacks, quite naturally, for this 23-year-old product of Tenares in the Dominican Republic. Just in the past week, Herrera had two of them.
Last Tuesday at Atlanta, he was staggered by three home runs in one inning. Herrera, who hadn't given up a run all season, was tagged with a devastating loss. He rebounded with a scoreless inning the next day in a win over the Braves.
But on Saturday at Boston, Herrera gave up a three-run homer that won it for the Red Sox. Once again, however, he proved resilient and returned with two shutout innings in Sunday's second game to help complete a doubleheader sweep.
"Herrera's fine. You just have those days," manager Ned Yost said. "He came back and got us through two innings and was throwing great, so I was proud of him."
So the early statistical line on Herrera reads 2-2 with two saves and a 5.79 ERA for 10 games. That's a far cry from last year's 76-game wrap of a 2.35 ERA with a 4-3 record and three saves. But there's a long way to go.
After the three booming blasts at Atlanta, there was a flurry of speculation that Herrera might be tipping his pitches. That theory since has been emphatically dismissed by Yost, Eiland and Herrera. Like real estate, it's location, location, location. And Herrera had wandered into the pitching slums.
"We are working on finishing my pitches, that's what we need to do," Herrera said. "Everything is up."
Indeed, Eiland believes the issue is mechanical and involves raising Herrera's arm slot a tad. Before his two shutout innings on Sunday, Herrera and Eiland were reviewing tapes of his delivery technique.
"He knows what he has to do," Eiland said. "It's just a small adjustment, nothing major, but if he doesn't make the small adjustment, then it becomes a major problem."
It's that location thing.
"Keeping them at the knee, that's the key," Herrera said. "High is no good, because they can hit them easy."
Sounds simple enough. Not so simple, though, when you're trying to make your arm and hand pinpoint a sphere of cowhide and red stitches traveling between 100 and 80-something mph within a tight rectangle 60 feet, six inches away from an unwilling adversary wielding a dangerous bludgeon. That, however, is something that Herrera has been able to accomplish often enough in his career.
"He has a way-above-average fastball and a way-above-average changeup. And his curveball is going to be above average once he gets comfortable throwing it and starts using it more," Eiland said.
"His stuff is plus-plus stuff. He throws 100 mph, and he can drop a changeup in there that acts like a split-finger fastball, that has late downward action and is 12 to 15 mph slower than his fastball. And he has the exact same arm action with that as he does with his fastball."
Herrera knows well that location, and alternating location, is a very valuable asset.
"He changes eye levels on his fastball," Eiland said. "Guys that throw hard, hitters can lock in on if that's all they throw, but he can change speeds. And you throw the curveball in on that mix and this guy's going to be really, really tough. He's really tough now."
This year, Herrera already has 15 strikeouts in just 9 1/3 innings.
Herrera came through the Royals' system like a comet in 2011, pitching at four levels -- culminating in the Major Leagues in September.
He made the club last year and the Royals initially steered him away from high-pressure situations, easing him into the more volatile drama that faces a big league relief pitcher. At first, Herrera sometimes tended to get rattled; now he's able to handle the stress. And in the parlance of the game, he always wants the ball.
Herrera's long-term future is probably as a closer.
"He's got that kind of stuff," Eiland said.
And that kind of mentality.
"Focus on the next game," Herrera said. "Whatever is past, is past."
Herrera was a skinny 153 pounds when he reported to the Dominican Academy at 17. Now, six years later, he's a solid 205 pounds on his 5-foot-10 frame. He's worked hard at building his strength. Herrera's learned how to warm up, gauging just when he's within a toss or two of being ready to enter the game.
One thing Herrera has always had, however, is the ability to throw a baseball very hard and very fast. That's something special.
"You are blessed," Herrera said.
So are the Royals. Check with Jeter.
Dick Kaegel is a reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.