Pitching to Royals center fielder Jarrod Dyson with runners at the corners, catcher Alex Avila tossed the ball back to Verlander, but it was deflected by the home-plate umpire and rolled back to the mound.
Thinking it was a live ball, he dropped to the ground to prevent the potential tying run from crossing the plate and rose gritting his teeth while head athletic trainer Kevin Rand sprinted out of the dugout.
"I think I gave myself a little bit of a scare and everybody else," Verlander said after the Tigers' 6-2 win. "It felt like it tried to pop out. I don't know what the feeling would be like."
Verlander said Rand didn't believe it "came out all the way." And with it being his non-throwing shoulder, the right-hander remained in the game and struck out Dyson and Alcides Escobar on 99- and 100-mph fastballs to end the inning.
Verlander also went on to throw 114 pitches and complete eight innings.
"I felt it for a little bit and then it went away," he said. "I got ice on it after the game and they said it will be pretty sore [Tuesday]."
On Tuesday, Verlander emerged from the training room sporting a red mark on the shoulder where he had been icing it. He said it felt as predicted, but after a few days of ice it should be back to normal.
"It was sore this morning, but it'll be fine," he said.