• Dress for the World Series with Royals gear
"Thank you," he said.
Now, with the World Series approaching -- Game 1 from Kauffman Stadium is Tuesday (7:30 p.m. ET air time on FOX, 8 p.m. game time) -- Herrera finally has a breaking ball he can trust. The 25-year-old right-hander refined it over the last three months of the regular season and went to it with conviction throughout the first two rounds of the postseason.
It gives Mets hitters something to think about aside from Herrera's 100-mph fastball and 90-mph changeup.
"If I execute it well, hitters can't really adjust," Herrera said, in Spanish, of his new slider. "They just don't expect it.
Herrera has thrown 31 sliders this postseason (Pitch-f/x sometimes identifies it as a curveball, but Eiland and Herrera said he's only throwing a slider). Ten have resulted in a swing and a miss and none have gone for hits. It's a pitch that has helped Herrera give up just one run on five hits and two walks in 8 2/3 innings this postseason, a stretch in which he's struck out 16 batters.
It's been a godsend for a Royals bullpen that is without closer Greg Holland.
"They're getting caught off guard," Eiland said. "Now word's out that he has it, but it still comes out of his hand like a fastball. That's why you're seeing some weak swings."
Herrera threw a slider in his early days in the Royals' system, but he scrapped it when he moved from the rotation to the bullpen in 2011. He intermittently went to a curveball as his third pitch, but it wasn't effective. With few exceptions, Eiland believes pitchers are either "born to spin a curveball or they're not." You need a loose wrist, you need to consistently get on top of the ball and you need a very particular release point.
The slider is thrown with the same grip Herrera uses to throw his two-seam fastball.
It came easy.
"I needed to get more swings and misses," Herrera said. "I always needed a pitch to get hitters out, and I feel like the slider has worked well for me. It's helped me a lot. Now the majority of strikeouts that I've gotten in these playoffs have been off the slider. It's a pitch that has helped me out a lot, and one that I think is going to help me out a lot in my career."
Alden Gonzalez is a reporter for MLB.com. Follow him on Twitter @Alden_Gonzalez and Facebook , and listen to his podcast. This story was not subject to the approval of Major League Baseball or its clubs.