Baltimore Orioles closer Zach Britton?ruptured his Achilles tendon Monday during a workout in California, general manager Dan Duquette confirmed to ESPN's Jerry Crasnick.

He is expected to miss up to six months, The Athletic is reporting.

"It's probably the most frustrating thing I've been experienced," Britton told MLB.com. "... This isn't something that's going to affect me long term. As soon as I have the surgery and rehab, I can get back to pitching like I can pitch. It's not career threatening or anything like that. But it's just going to be a real grind. I was really frustrated because I was feeling good with the forearm and the knee. I was about to throw bullpens. I was right where I wanted to be."

The left-hander had been the subject of trade rumors because he will be a free agent at the end of the 2019 season. He was set to earn more than $12 million in arbitration.

Britton, 29, was the most dominant reliever in baseball in 2016. He led the league with 47 saves and had a 0.54 ERA and 0.836 WHIP. He was an All-Star and finished fourth in Cy Young voting.

But injuries slowed him last year. An MCL strain in his left knee required platelet-rich-plasma treatment.

He was limited to 38 games and had a 2.89 ERA, 1.527 WHIP and 15 saves.