"I think he did it as he pushed off the wall, he sprained it," manager Ned Yost said. "I was just watching the ball. I saw him push up, go after it and saw it was a home run. Then I took my attention off of him. Then I looked and he was squatting down."
Trainer Nick Kenney tended to Dyson, who returned to the dugout with a limp. There was no immediate indication on how long Dyson might be out. He will be re-evaluated on Friday in Oakland.
"I think his foot got stuck in the wall when he jumped," right fielder Lorenzo Cain said. "Hopefully, he's OK because we definitely need him out there."
Dyson, leading off for the Royals, had an RBI triple and scored after drawing a walk. He's batting .268 in 18 games.
Dick Kaegel is a reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.