Jeff Fulchino, also a right-hander, was optioned to Omaha. He pitched three innings on Sunday as one of four relievers used after starter Kyle Davies was unable to get out of the second inning.
Peralta was expected to report in time for Monday night's game against the Colorado Rockies.
After a string of seven straight games in which the Royals' starting pitchers had gone seven or more innings, the bullpen was on scramble alert during the weekend series against the San Francisco Giants. The relievers worked a total of 15 1/3 innings.
Fulchino appeared in six games with no record and a 9.00 ERA. In his three innings during Sunday's 11-10 victory, he gave up four runs on seven hits and three walks. Manager Trey Hillman noted, however, that Fulchino at least kept the ball down.
"Overall, we were pretty pleased with what he did, but the simple need we have is making sure we're protected for this series, and specifically for this game," Hillman said. "Because we've gone through the bullpen quite a bit, as you usually do when you get your starter out in the second inning."
Peralta was recalled for the second time this season. In his first stay, he worked in 18 games and had an 0-2 record and a 5.64 ERA. In his two stints with Omaha, he did not allow a run in 18 2/3 innings and had a 1-0 record and two saves.
Hillman said that Peralta needs to demonstrate better location of his pitches in this go-round with the Royals.
"He left both fastballs and secondary pitches out over the plate," Hillman said. "He's just got to be able to locate and get ahead in the count. He wasn't able to do that. I know before this season he's had a pretty good history of doing that, so hopefully, he can find the consistency there."
Dick Kaegel is a reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.