But Perez was smiling afterward in the clubhouse and had a one-word answer for his condition.
"Bueno," he said.
"He's fine," manager Ned Yost agreed. "He just got cramps in both his legs. They came in and made him drink a bunch of fluids and gave him an IV and he's fine."
Could he be back in the lineup on Tuesday night?
"Oh, sure. You know that," Perez said.
Moustakas was drilled between the eyes when Victor Martinez's chopper took a bad hop in the ninth inning.
"I figured in honor of the World Cup, I'd try to head-butt one back to the dugout," Moustakas said.
The ball didn't go that far, but did bounce back to pitcher Donnie Joseph at the side of the mound. It went for a single just before J.D. Martinez whacked a grand slam.
"I've never played soccer before," Moustakas said.
Dick Kaegel is a reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.