Dotel injured his oblique on his last pitch in Surprise, Ariz., against the Rangers.
"I thought it wasn't something bigger," Dotel said. "I thought it would go away, but it's still hanging out. I'm looking forward to see it go away. I hope [I'm not out of action] for long."
Dotel threw on a flat surface on Wednesday, but he suffered some discomfort when throwing at a longer distance.
"Not good," Dotel said on how he is feeling. "I'm still feeling it a little bit."
"He wasn't in a lot of discomfort, but it really wasn't well enough for him to stay off the DL," manager Buddy Bell said. "We just shut him down and made the decision."
Bell said an MRI on Tuesday showed no tear, but "a small hot spot, which is irritable for him."
"I think it's the right thing to do with Dotel," Bell said. "I think maybe in three or four days he might be ready, but I don't think that was worth the risk. That's the reason we put him on the DL right now, so it would not be a chronic issue as the year went on. It's unfortunate. We don't think it is something that is going to linger."
The injury is on Dotel's non-throwing side.
"That is a little bit unusual, but in the violent way he throws, it's understandable," Bell said.
David Riske, who has 16 career saves, will assume the closer's role, Bell said.
"David has had some experience closing," Bell said. "That is the biggest reason why he's in that spot right now. If we've got somebody going good going into the ninth, we might just leave him in rather than bring David in."
The Royals purchased Jason Standridge's contract from Triple-A Omaha to take Dotel's spot in the bullpen.
"I'm excited about the opportunity, no matter how it happened," Standridge said.
Standridge was with the team in Houston for the final two Spring Training games and then went to Birmingham, Ala., to retrieve his car and drive it to Omaha. He did not make the final part of the journey.
"They said just come here and stay here because there's a possibility they would put me on the roster," Standridge said. "It's about a 12-hour drive from Birmingham and my dad came with me to keep me company. We spent last night in a [Kansas City] hotel."
Standridge was 1-2 with a 4.35 ERA in Spring Training, allowing five earned runs and 12 hits in 10 1/3 innings.
"He pitched well enough to make our club, but we had some other guys that pitched a little bit better," Bell said. "His sinker got exceptionally better as the spring went on. He used his sinker very effectively, which made his breaking ball better."
Standridge, a 28-year-old right-hander, was 1-1 with a 4.82 ERA in 21 relief appearances last season with the Reds. He has also pitched for the Rangers and Devil Rays, compiling a 3-8 record with a 5.64 ERA in 76 games, including nine starts, in the Majors.
Leo Nunez, who suffered a fractured right wrist when he was hit by a line drive on March 9, was transferred from the 15-day to the 60-day DL to make space for Standridge on the 40-man roster.
Off the charts:
Channel 38 pulled an 8.3 rating for the Royals' Opening Day victory over the Red Sox. It was the highest rating for a Royals' game since July 20, 2003. The 2006 season opener -- a loss to the Tigers -- drew just a 4.8 rating.
The temperature for Wednesday's first pitch was 42 degrees, a 32-degree drop from the season opener. It was 79 when the game began Monday.
Red Sox right-hander Daisuke Matsuzaka will make his Major League debut opposite the Royals' Zack Greinke in a 1:10 p.m. CT contest on Thursday.