ST. LOUIS -- The Royals on Thursday placed struggling right-hander Trevor Cahill on the 10-day disabled list because of right shoulder impingement syndrome, and they recalled right-hander Kevin McCarthy from Triple-A Omaha.
Cahill pitched on Wednesday in the Royals' 8-5 loss to St. Louis and was ineffective for the third straight start since being acquired from San Diego. Cahill gave up three runs and walked five in 2 1/3 innings.
"He's been pitching through it," Royals manager Ned Yost said. "Last night he just got fatigued pretty early.
"It's time to take a step back and let it get strong again and start moving forward."
Cahill left the team Thursday and flew back to Kansas City to have an MRI exam.
"We just want it double-checked to make sure it checks out," Yost said.
Royals general manager Dayton Moore said on the day the Royals acquired Cahill, Ryan Buchter and Brandon Maurer from the Padres that his medical staff was satisfied with the reports on Cahill.
Yost reiterated that position on Thursday.
"We knew [about Cahill's shoulder fatigue] going in," Yost said. "Really, the majority of it is just rotator cuff weakness. The shoulder is structurally sound, other than the normal wear and tear of a veteran pitcher."
Cahill's next scheduled start would have been Monday in Oakland. That spot is now open, but it would seem logical that right-hander Jake Junis would be called up from Omaha then. Junis pitched eight strong innings Sunday night against Seattle, allowing one run and four hits.
"Could be [Junis]," Yost said. "Probably would be, but we haven't made a decision yet."
McCarthy has made 16 appearances for the Royals this season and posted a 2.14 ERA.
Jeffrey Flanagan has covered the Royals since 1991, and for MLB.com since 2015. Follow him on Twitter @FlannyMLB. This story was not subject to the approval of Major League Baseball or its clubs.