Pitcher Luke Hochevar was recalled from Triple-A Omaha to take Soria's place on the roster and Sidney Ponson's place in the starting rotation. Hochevar will start on Tuesday night at Oakland, moving Ponson into the bullpen.
Hochevar had a 5-0 record in six starts for Omaha with a 0.90 ERA.
There was no immediate estimate on how long Soria might be sidelined. He last pitched on Thursday against Seattle in a rocky but successful 29-pitch outing. His DL stay is retroactive to Friday.
"We've been going day-to-day as you know. It's a little bit of a strain of the rotator cuff that he's going through," manager Trey Hillman said.
Soria last season was one of the game's premier closers with 42 saves, the second-most in the American League. He had just three blown saves along with a 1.60 ERA and opponents hit just .170 against him.
Now, Hillman said, the Royals' closer role will be handled by a "committee," although right-hander Juan Cruz might be near the top of the list. Also likely to be in the mix are right-hander Kyle Farnsworth and left-hander Ron Mahay.
Soria said his shoulder did not bother him during his long inning against the Mariners last Thursday but it was sore the next day.
"It's not going away so I'm going to have to take time to get ready for an entire season. I think it's too early in the season to be pitching like that," Soria said.
"I think the better thing is to be put on the DL and see what happens after the 15 days."
The earliest that he could return would be May 23 at St. Louis. There also is the possibility that he would spend time in the Minors on an injury rehabilitation assignment.
Soria accompanied the Royals to Oakland for a day off on Monday followed by a two-game series. He's confident he'll be able to return on time.
"Oh, yeah," Soria said. "I think I can be back in the 15 days. It just needs rest. We'll take care of that and see what happens."
Soria has appeared in just eight of the Royals' 30 games. He had seven saves in seven chances, a 1-0 record, a 2.08 ERA and 10 strikeouts in 8 2/3 innings. His on-and-off absence has created a noticeable gap in the bullpen.
"For the last two weeks, we've been in the same situation pretty much," Hillman said. "I was trying to make sure I didn't do anything to increase any of the inflammation that he's had. So at some point you have to decide if you want to get it calmed down now rather than possibly going two or three days without him."
The ailment apparently first surfaced on April 18 when he was warming up in the bullpen at Texas to possibly replace Zack Greinke in the ninth inning. He did not and Greinke finished with a shutout. The pain is in back of Soria's shoulder.
"It's the same place and it's not going away," Soria said.
The move to bring in Hochevar to bump Ponson out of the rotation was something of a surprise. Ponson had pitched well in his last outing, gaining his first victory. Now Ponson will operate out of the bullpen.
"Sid obviously will give us another ground-ball guy and we'll use him as needed; he's resilient," Hillman said. "We'll get Hoch up here and see how he's going. He's coming off one of his best outings so far this year and, hopefully, that'll help our team win ballgames. And we'll see where we sit when we get Jack [Soria] off the disabled list."
Hochevar, in six games, has 30 strikeouts and only 10 walks in 40 innings with 28 hits allowed. He's given up six runs, four of them earned. Although he didn't get a victory, his last outing was especially eye-catching. Against Memphis, Hochevar threw eight shutout innings with five hits, no walks and nine strikeouts. After he left the game, Omaha lost, 3-2.
So that was a compelling reason for the Hochevar-Ponson switch.
"We just felt like it would keep our club strongest and being able to win ballgames, both out of the rotation and in the bullpen," Hillman said.
The loss of Soria put an added damper on a third straight loss to the Angels.
"We were able to get through a small stretch without him but, obviously, 15 days is a lot longer," third baseman Mark Teahen said. "Hopefully, he can get whatever he needs taken care of but we've built a strong bullpen and hopefully we can weather it."
"That's obviously never a good thing," first baseman Mike Jacobs said. "He was one of the best closers in the game last year. Being without him definitely hurts us but, hopefully, we've got enough guys in here that can take up the slack and turn this thing around."
Dick Kaegel is a reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.