Nathan (elbow) said he felt a pop in his right arm during his rehab appearance with Triple-A Toledo on Wednesday, MLive.com reports. "It feels like I broke my arm," Nathan said. "I never have broken my arm, but I would assume this is what it feels like." Nathan was scheduled to throw 25 pitches in what was expected to be his lone rehab outing, but the setback forced him off the hill after just 10 pitches. It doesn't sound good for the 40-year-old, but Nathan is expected to undergo a series of tests, including an MRI, to determine the true extent of the issue. Joakim Soria will continue to close for the Tigers for the time being.