BOSTON–Oriole pitcher Bruce Zimmermann sprained an ankle in a training room accident, according to manager Brandon Hyde, and will remain on the 10-day injured list. The left-hander has missed nearly two months because of left biceps tendinitis.

“He sprained his ankle doing some sort of exercise the last couple of days,” Hyde said. “He was definitely a possibility to start coming up. With the sprained ankle, he’s not going to.”

Zimmermann was expected to start on Sunday against the Red Sox. Left-hander Keegan Akin, who allowed six runs on seven hits in three innings on Tuesday night against Detroit, will make the start.

Mountcastle gets closer: First baseman/designated hitter Ryan Mountcastle is eligible to come off the seven-day concussion injured list on Sunday. Hyde said he won’t but that he’s improving and probably won’t need a rehab assignment.

“I’m hoping he can just come back and join us,” Hyde said. “It’s really going to be dependent on how long he’s going to be out. He’s made huge strides the last few days. Every day has been better. He ramped up his activity today. He responded extremely well. He’s going to do some baseball activity stuff starting tomorrow, see how he reacts to that. Hopefully, it’s not too much longer after that.”

Notes: Cedric Mullins, who left Friday night’s game after batting in the top of the eighth, isn’t in the lineup against Boston left-hander Chris Sale. “A day off. He’ll be ready to come in off the bench,” Hyde said. “I just wanted him to rest a little bit to start the game.” … Left-hander Zac Lowther, who’s on the minor league injured list because of a strained left shoulder, will make his first rehab start in Sarasota on Monday, Hyde said. Lowther will pitch for one of the Florida Complex League teams. … Right-hander Hunter Harvey, who’s on the injured list because of a right lat strain, threw to hitters in Sarasota on Saturday. “He’s progressing well,” Hyde said. “We’re hoping he’s going to leave Sarasota soon, go on a rehab assignment, but he’s getting very close.”