Ellington has been diagnosed with biceps tendinitis and will not undergo an MRI, Clark Spencer of the Miami Herald reports.
While Ellington didn't complain of any injury after his Grapefruit League debut over the weekend, diminished velocity and a lack of control prompted the Marlins to send the 27-year-old for some tests. He'll now rest up until the soreness subsides. It's unclear how long this will set Ellington back, but there will likely be an update on his status once he's able to resume a throwing program.