"Tough lefty on the mound, and I was trying to get something out over the plate," Moustakas said. "[Alvarez] came with a fastball, and I was able to put the barrel on it. I'm seeing the ball pretty good right now. I had some pretty good at-bats earlier in the game, but just didn't have anything to show for it."
It was the 300th career RBI for Moustakas, who blasted his third career go-ahead homer in the eighth inning or later. He has also homered in consecutive games for the eighth time in his career.
Royals closer Kelvin Herrera pitched a clean ninth to pick up his second save of the season.