"I was working on a breaking ball, my curve," he said. "It was pretty good and I'm still working on it, getting better on that pitch. I'm going to have three pitches this year -- changeup, breaking ball and fastball."
The curve must have worked pretty well because Herrera gave up just two earned runs in 9 1/3 innings, while registering 14 strikeouts.
Now, Herrera can turn his attention to improving on his up-and-down 2013 season for the Royals.
"We're going to play hard this year and we're going to try to win our [American League Central] division," Herrera said. "We've got a pretty good group of guys, everything's good in the clubhouse and that's the most important part because you've got to be good teammates, and we are that."
Dick Kaegel is a reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.