CHICAGO — Orioles right-hander Zach Eflin underwent season-ending Tommy John elbow reconstruction surgery, the team said Wednesday, which concludes Eflin’s return to Baltimore after just one start.

Eflin left his first start of the season after 3 2/3 innings last week with right elbow discomfort, and he quickly landed on the 15-day injured list. After receiving an MRI, Eflin flew to Texas for a second opinion on the imaging from Dr. Keith Meister, a foremost expert on baseball elbow injuries.

On Wednesday, Eflin underwent the surgery, which the Orioles described as successful. Meister performed the operation.

When Eflin was moved to the 60-day injured list this week to make room on the 40-man roster for another pitcher, it was an indication the prognosis for him was poor.

“I feel for Zach,” manager Craig Albernaz said last week. “The whole coaching staff, the whole team, you just feel for him. Heart hurts for him. You never want to see anything happen to any player, especially someone like Zach.”

This is another massive setback for Eflin, who returned this spring healthy after an August back surgery. He spoke of his improved quality of life, the ease with which he could pick up and play with his children following back surgery. The operation, of course, helped his pitching.

But Eflin has another long recovery period ahead of him.

“That’s tough. Any time you see any one of your guys feel something barking, it’s always you’re hoping for the best and that — it straight up stinks,” first baseman Pete Alonso said at the time of the injury. “Ef’s a good dude and a really, really hard worker. I mean, he’s a guy who I hope everything is OK. Hopefully, ’cause we need him, for sure.”

Baltimore re-signed Eflin on a $10 million contract that includes a mutual option for next season. With performance incentives, the deal could have maxed out at $30 million.

Meister has performed many of the elbow surgeries for Baltimore’s pitchers in recent years, including Félix Bautista, Kyle Bradish and Tyler Wells.

The Orioles are testing their rotation depth just four series into the season. Left-hander Cade Povich, who pitched in relief against the Pittsburgh Pirates, will start Sunday against the San Francisco Giants. Right-hander Brandon Young excelled in five innings against the Chicago White Sox on Monday, but he was optioned for a fresh arm.

Right-hander Dean Kremer should be in the mix soon. He is making his second start of the season for Triple-A Norfolk on Wednesday.

This article has been updated.