With the Royals leading, 2-1, the Astros' Chris Snyder led off with a single against closer Jonathan Broxton. Snyder was replaced by pinch-runner David Carpenter, a relief pitcher with decent speed. On a 1-1 count, pinch-hitter Matt Downs hit a sharp ground ball right at third base.
Moustakas, playing on the line to prevent extra bases, made a sliding stop and threw out Carpenter at second for the first out of the inning.
"Great play. That's a great play," Yost said. "That changes a lot of things if he doesn't make that play. To get the lead runner at second base was good, too."
Yost was a bit worried about the prospect of facing second baseman Jose Altuve, batting .313 overall, with runners in scoring position. Moustakas' play allowed the Royals to stay in double-play defense, though Altuve still singled off Broxton to put runners on the corners with one out.
Broxton then fanned Bryan Bixler and got Jordan Schafer to fly out for his 18th save and second in as many games.
Moustakas downplayed his big stop in a key situation.
"Brox made a great pitch," Moustakas said. "I just tried to get in front of it."