"He was throwing up all night," manager Ned Yost said before the rubber game.
Moustakas' left-handed bat was supposed to be in the lineup against Rays right-hander Alex Cobb, but Moustakas' right-handed counterpart, Danny Valencia, took his spot.
"Moose is in the training room looking like death warmed over," Yost said.
Left fielder Alex Gordon was also scratched because of a sprained right wrist and starting pitcher Jason Vargas was in the hospital, awaiting appendix surgery.
"I heard [Vargas] was sick, then Moose came in sick and now I'm like, 'Oh, Lord, I hope this isn't an epidemic,'" Yost said. "But everybody [else] is doing OK."
Dick Kaegel is a reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.