WASHINGTON (AP)Washington Nationals reliever Sean Doolittle will undergo an internal brace procedure on his left elbow, ending his season.

The left-hander, who has been on the injured list since April 20 with an elbow sprain, is expected to be out between five and six months. Doolittle underwent platelet-rich plasma and stem cell injections, but began feeling the same soreness in the last week as he did when he was first injured.

”There’s still too much instability in the elbow, there’s too much instability being caused by that UCL not being healed enough and not being strong enough,” Doolittle said Friday. ”At this point, I just want to go in and get it fixed. I want to get to the root cause of it.”

The internal brace procedure repairs an existing ulnar collateral ligament instead of the full reconstruction involved in Tommy John surgery. It is a less invasive option, which also allows for a quicker recovery.

”He wants to pitch again and he’s hoping this will help him come back sooner,” Washington manager Dave Martinez said.

A two-time All-Star, the 35-year-old Doolittle threw 5 1/3 scoreless innings in April before going on the injured list. He said he considered the internal brace surgery then, but ultimately wanted to pursue rehab options that could allow him to return this season.

With that possibility gone, the pending free agent hopes to be ready for spring training next year.

”I don’t feel good about getting surgery (but) I feel good that this has been the right course of action for me right now at this point in my career, at this point in this process with my elbow,” Doolittle said. ”As far as I’m looking at it, 2023 starts right now. I’m viewing this as a long, extended ramp-up into the season last year.”

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