ANAHEIM — The forearm injury landed Matt Shoemaker on the disabled list last month has returned, stalling his progress and leaving the Angels to schedule him to see a nerve specialist to help solve the mysterious issue.

“Just extremely frustrated,” Shoemaker said on Thursday. “Everything felt great until Sunday when I ramped up for my bullpen. I felt phenomenal. That’s what’s so frustrating, that it hasn’t gone away yet, that the symptoms came back.”

Shoemaker, who has pitched just once this season, had an Electromyogram test on Monday. General Manager Billy Eppler said it showed some healing, but not enough for his throwing program to proceed. He is now headed to Missouri sometime next week to see a peripheral nerve specialist, Eppler said.

“It’s really hard to put a finger on how you feel emotionally on this, beside disappointed,” Eppler said. “The person shouldering the biggest disappointment is Matt right now. We’re missing a key part of our rotation. This is frustrating for us and frustrating for Matt. Hopefully, we’ll have better news next time.”

Shoemaker threw in the bullpen twice over the weekend, but the symptoms returned during the second session.

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Hoornstra: ‘What even are positions anyway?’ The answer is complicated Last year Shoemaker went on the disabled list in June with forearm tightness, and his rehab progressed normally all the way until he pitched in a minor league game in July. After increasing his intensity to game speed, though, he had a setback, and he ended up having surgery to have the radial nerve released.

Eppler said the tests so far have shown that the current injury seems to be different, even though it’s still nerve-related. In both cases, Shoemaker was proceeding without difficulty in his rehab, only to have a setback when he increased the intensity.

“Nobody is working harder than Shoe,” Manager Mike Scioscia said. “I know its a very frustrating process. We’ll just let our medical staff evaluate it and see what the next step should be.”

Even without Shoemaker, the rotation has stabilized with the improvement of Andrew Heaney, the emergence of Jaime Barría and the mostly strong work all season from Garrett Richards, Tyler Skaggs and Shohei Ohtani. Nick Tropeano is expected to come off the disabled list on Saturday.