"He's fine, just a bruise," Yost said. "The trainers were a little nervous at the beginning because it was getting sore. They didn't know what it was, but they came in and X-rayed it, and everything came up clean."
Moustakas was injured in the second inning when a grounder by Cardinals catcher Yadier Molina took a high hop and nailed the third baseman near his throat/chest.
Moustakas went 1-for-2 at the plate, including a double in the first inning. He leads the Royals with a .335 average.
As to Moustakas' availability for Sunday's I-70 Series finale, Yost left it open.
"It's pretty sore," Yost said. "We'll have to wait and see how he feels tomorrow."
Colon singled to center field in one at-bat prior to the rain delay. He is batting .283 with 17 hits and four RBIs in 20 games this season.
Jordan Wilson is an associate reporter for MLB.com.