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It’s been discussed a lot over the past few days, but Franklin Pérez is hurt again, and this time, he is finally having surgery.

Pérez, once the prime return piece in the Justin Verlander trade, went on the injured list with a “right shoulder capsule defect” before visiting Dr. Neal ElAttrache in Los Angeles. The Tigers announced that Pérez will have surgery, and Pérez was also waived as a means of being removed from the 40-man roster before re-signing with the Tigers on a minor-league deal.

Pérez’s injury history has included a lat strain, right shoulder capsular inflammation and “arm weakness,” only part of a long history of somewhat vague injuries that have limited Pérez to 27 innings since he was acquired from the Astros organization in 2017.

The Tigers did not announce the exact nature of Pérez’s surgery, and manager A.J. Hinch did not give a specific timetable for Pérez’s recovery other than noting he will be out for “a while.”

Dr. Trong Nguyen, MD, FAAOS, a sports medicine specialist and orthopedic surgeon at MemorialCare Orange Coast Medical Center in Fountain Valley, Calif., is not treating Pérez but provided some insight that could help make sense of the injuries.

“There’s a lot of subtlety to the shoulder, especially when it comes to overhead athletes,” Nguyen said. Nguyen declined to give details on Pérez’s injuries without a copy of his MRI but said the shoulder capsule is “made of dense tissue that holds the shoulder in place,” sealing the joint off from the rest of the body. Capsular defects can break down into various categories of injuries. There could be traumatic injuries, where something tears off the anterior portion of the shoulder. There could be “multidirectional instability,” common in overhead athletes. And Nguyen speculates Pérez’s condition could be related to micro-injury that has added up over the years.

“Over time, the tissue tends to wear down, and the capsule, when it wears down, tends to become insufficient or deficient,” Nguyen said. “People can have problems with throwing, especially high-end throwing or high-end pitching, especially in the anterior capsule because there could be pain or microinstability that affects their performance. In those situations, if non-operative management doesn’t work, then surgery to tighten up that capsule can be performed.”

The mystery around Pérez’s shoulder also isn’t necessarily a surprise. Diagnostic issues are common with these types of injuries. In 2019, the Tigers had stated there was no structural damage to Pérez’s UCL or rotator cuff.

“Pitchers require so much range of motion because of the pitching motion itself that it puts a lot of strain on the capsule,” Nguyen said. “A lot of time the MRIs can be inconclusive, meaning they don’t show any structural defects, and the injury could be on a microscopic level that you don’t necessarily see on an MRI. Making a diagnosis, you kind of have to be really familiar with shoulder mechanics, and I’m sure the guys that are looking at him are top-end shoulder specialists.”