"He's got a tight lower back, that's why he wasn't moving very good yesterday," manager Trey Hillman said.
With an open date Thurday, followed by a home series that opens Friday against the White Sox, Hillman figured back-to-back days off would help DeJesus.
"I don't think it's serious; I think it's just muscle tightness," Hillman said. "Hopefully, we'll get a refreshed guy back day after tomorrow."
With DeJesus out, the Royals had Mike Aviles in his normal leadoff spot against Oakland with Mitch Maier in center field batting second.
Jose Guillen was back in right field despite problems with his left hip flexor.
"Straight on, he seems to be OK, but anything that requires him to go side to side, he's tentative," Hillman said. "At the plate, his swings look max effort. My biggest worry is getting out of the box. I told him to be real careful, I don't want him trying to beat anything out."
Hillman explained that Guillen was experiencing problems primarily in his left leg now as opposed to his right leg previously.
"It's something that may have happened because of past compensation on the other, I don't know," Hillman said. "It's certainly not something we want to extend on a long period of time."
Dick Kaegel is a reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.