Herrera stirred up plenty of dislike from A's fans during the first series between the Royals and A's in Kansas City when he threw a 100-mph pitch behind Oakland's Brett Lawrie. Herrera, after being ejected, pointed his index finger to his head as he glared at the Oakland bench, later saying it meant, "Think about it."
So A's fans were ready for him Friday night in the eighth inning. Herrera came in and immediately was showered with boos, likely the loudest boos Herrera has ever had directed at him.
But Herrera didn't seem to mind.
"I was expecting that," he said, shrugging his shoulders. "It doesn't bother me. That's my job."
Herrera said the booing didn't intimidate him at all.
"It's normal," he said. "It's OK. It's part of the job. I knew it was coming. The fans know of us. They pay attention."
Herrera went about his business, retiring the A's in order in the eighth.
"I expected [the booing] and I kind respected it," manager Ned Yost said. "That's what's cool about this game. But Kelvin didn't care at all. He came in banging strikes and throwing 98."
Jeffrey Flanagan is a reporter for MLB.com. Follow him on Twitter at @FlannyMLB. This story was not subject to the approval of Major League Baseball or its clubs.