PHOENIX — The Orioles are set to lose their best starting pitcher for at least a week as Zach Eflin is being shut down with a low-grade lat strain, manager Brandon Hyde said after Tuesday night’s 4-3 loss.

The injury is another blow for an Orioles staff that has already lost right-hander Grayson Rodriguez to begin the year. Baltimore is also waiting on the returns of right-handers Kyle Bradish and Tyler Wells deeper into the season after their 2024 Tommy John elbow reconstruction surgeries.

Hyde said that after a week the organization will reassess Eflin’s condition, and hopefully Eflin will be ready to begin throwing again.

The right-hander cruised through six innings against the Diamondbacks on Monday night. He had retired eight straight batters and thrown just 73 pitches by the end of the sixth, but he reported shoulder fatigue to Hyde and the Orioles opted to be cautious.

Eflin underwent an MRI on Tuesday. Baltimore brought right-hander Colin Selby to Arizona as part of the taxi squad in case a move was necessary. Hyde said before the game there was optimism based on how Eflin’s shoulder felt Tuesday morning when he awoke.

Since Eflin arrived in a trade last year, he has been critical. The righty, who celebrated his 31st birthday Tuesday, pitched to a 2.60 ERA in nine starts with Baltimore last year. So far in 2025, Eflin has completed six innings in all three starts.

Hyde said a decision has not yet been made on who will take Eflin’s spot if a stint on the injured list is needed. There’s a possibility Baltimore could skip Eflin’s place in the rotation and roll with four starters for the time being, because there are off days Thursday and Monday that would allow their starters to pitch on normal rest. That would buy the Orioles and Eflin time.

If the Orioles decide a replacement starter is needed, they could turn to right-hander Brandon Young. The 26-year-old is already on the 40-man roster. He has also gotten off to a strong start for Triple-A Norfolk with two unearned runs against him in 11 1/3 innings.

Another option is right-hander Cody Poteet. The Orioles traded cash to the Chicago Cubs for him in March. Poteet started four games last year for the New York Yankees and posted a 2.22 ERA in 24 1/3 innings.

Earlier this week, Hyde said it felt as though the Orioles were “dodging and weaving” all the injuries. At this point, most of the punches appear to be connecting. The Orioles are also without outfielder Colton Cowser (fractured thumb) and right-handed reliever Andrew Kittredge (knee surgery).

“I’ve been on some really good teams the past few years that went through the same thing,” right-hander Charlie Morton said. “We lost some really good players in Atlanta and still were able to accomplish some really good things. ... All teams have injuries. It’s just, as an individual, stepping up and doing my job.”

Morton, who has allowed four or more runs in all three of his starts, said he needs to “get going.” There are multiple reasons for that, but one is to cover for the absence of a steady arm.

“Hopefully he doesn’t miss much time,” Morton said.