Unusual injury to keep Kohei Arihara out of Texas Rangers rotation at least 12 weeks

Right-hander Kohei Arihara, one of the Texas Rangers’ key offseason signings, could miss the rest of the season because of an aneurysm in his shoulder that requires surgery.

The condition is similar to thoracic outlet syndrome, general manager Chris Young said, but it does not require the removal of a rib. Arihara will need at least 12 weeks to recover, which would put the earliest possible return date in late August or early September.

Young said that Arihara had been dealing with symptoms on a timeline that correlate to his poor performances, which were compounded by a bruised middle finger that put him on the 10-day injured list. Symptoms, though, intensified the over the past 10 days.

“Obviously a very disappointing outcome for both Kohei and the Rangers,” Young said. “We wish him the best and we are very confident in medical treatment he’s received ... and we’re expecting him to have a full recovery.”

The procedure will be performed Thursday in Dallas by Dr. Greg Pearl, a renown thoracic surgeon who specializes in thoracic outlet syndrome. Young said that if left untreated, the aneurysm cause much greater issues than missing three months of a baseball season.

Arihara, who was lured away from Nippon Professional Baseball on a two-year, $6.2 million contract, fully supports the decision to have surgery.

“We’re very fortunate that this was caught early and that we didn’t continue to push it with him,” Young said. “The medical team did a great job, Kohei’s on board and understands the severity and the consequences of not having the surgery. So, he’s ready to get it done.”

Arihara opened the season with a 2.21 ERA after his first four starts, but he posted a 10.29 ERA over his final four outings. The first of those came April 25 on a chilly day at Chicago, but the Rangers believed the cold and the middle finger were factors more than anything else.

But he continued to experience issues in his hand, a sure symptom of thoracic outlet syndrome. Young said that Arihara has an arterial condition rather than a neurogenic condition that necessitates extracting a rib to restore normal sensations down the arm.

“I think if you’re having thoracic outlet surgery, my understanding is this is the type that is that you would want to have,” said Young, who underwent thoracic outlet surgery in 2013.

Left-hander Hyeon-Jong Yang, who pitched well Wednesday as the Rangers were no-hit by Corey Kluber, is expected to fill in for Arihara, though others will likely receive opportunities over the course of the next three months.

Among those in the minor leagues who could be promoted is left-hander Wes Benjamin, who was on the Opening Day roster and made a spot start last weekend at Houston.

The Rangers are open to letting Arihara pitch again this season, but they have no intention of pushing him.

“His health is most important for us and we’re prepared to fully support him in that recovery,” Young said.