Medlen then fooled the dangerous Bryce Harper, who popped up. But the popup floated and dropped into center field for an RBI hit.
Then came three straight doubles and Medlen's day went completely awry.
"From the get-go, I felt good in the first inning," Medlen said. "The errors, those things happen. I need to do a better job of containing those things. The defense picks up the pitchers all season long. So I need to pick up our guys when things don't go right."
Medlen gave up six runs in the first, three earned. He did toss a 1-2-3 second inning, but loaded the bases in the third inning with none out, and manager Ned Yost pulled him.
Medlen was charged with nine runs, six earned.
"I felt great out of the windup, but when I went to the stretch, I got too quick," Medlen said. "I couldn't stop the bleeding in that first inning. I'm making pitches that are pretty good when they leave my hand, but they get fouled off. Just a bad day."
Medlen said he wasn't distracted by the errors.
"No, we're all human," he said. "It happens. My job is to pick it up for them. I didn't do it.
"It's just one of those really frustrating days that is now over."
Jeffrey Flanagan has covered the Royals since 1991, and for MLB.com since 2015. Follow him on Twitter @FlannyMLB. This story was not subject to the approval of Major League Baseball or its clubs.