Down, 3-0, in the sixth with two out, Hosmer guessed right.
"He'd been throwing a lot of first-pitch fastballs," Hosmer said, "and I just decided to be ready for it and jump on it. And I did. Got a good swing on it."
The ball was scorched over the left-field wall, but Hosmer said there was no real intent to go the other way.
"I just wanted to go up the middle," he said. "Just go up the middle and get a good swing, and stay with it."
The homer was Hosmer's 17th this season. Up next came Kendrys Morales, who reached for an outside splitter and blasted it over the left-center-field wall.
"I had to reach for it," Morales said through interpreter Pedro Grifol. "But I got the barrel of the bat on it. I got the fat part on it and it went."
It was Morales' 22nd homer of the year as he took over the team lead. But that was it for the Royals' struggling offense.
"I don't think we're swinging the bats badly," manager Ned Yost said. "We have had bad at-bats, but we're not swinging poorly.
"We had back to back home runs with Hoz and Morales. And Morales just missed another one."
Jeffrey Flanagan is a reporter for MLB.com. Follow him on Twitter at @FlannyMLB. This story was not subject to the approval of Major League Baseball or its clubs.