ElAttrache said the injury is unrelated to the surgery he performed on Kemp last year to repair a torn labrum and a frayed rotator cuff.
Manager Don Mattingly said he's optimistic that Kemp, who received a cortisone injection Friday night, would be on the DL the minimum 15 days.
"I think so," Mattingly said. "But I don't want to go out on a limb. I think 15 and he'll be ready to go, but I didn't think he would be disabled."
Mattingly initially said he didn't think Kemp would need a rehab assignment, then backpedaled and said "possibly."
Kemp felt pain in the shoulder on a swing and miss Friday night against the Giants. Mattingly said Kemp also had discomfort in the AC joint in earlier this year and last year.
Ken Gurnick is a reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.