"I'm really fine," Perez said through a team spokesman.
Perez was struck behind the left ear by a 2-1 pitch, a breaking ball, by Padres pitcher Johnny Barbato in the third inning. After going down into the dirt, Perez got up and left the field under his own power, rubbing his head next to the ear. He went into the dugout to be checked by team trainers.
Then, after the top of the fourth, Perez emerged from the dugout pulling his equipment bag and waving and smiling to the crowd as he made his way down the right-field line toward the clubhouse.
"He's doing fine," Royals pitcher James Shields said. "It just kind of rung his ears a little bit, but he's doing pretty good. Any time you get hit in the head, it's scary, but he's fine."
Perez was replaced by Minor League catcher Jesus Flores.
Last season, Perez spent a week on the disabled list after sustaining a concussion when a foul ball struck his mask and jarred him in a game against the Mets at Citi Field.
"It's always scary, but it's even more scary when it's Sal and you know his history," manager Ned Yost said. "It was a slower-type breaking ball, it wasn't a fastball. He was fine."
Dick Kaegel is a reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.