"The unfortunate part is he's going to be out for a while," Trembley said. "We don't expect that he'd be able to play at the earliest until mid-September. He's out for an extended period of time. I think what he'll probably end up doing is go home for a while. Then he can do some rehab in Florida and eventually get to [Instructional League]."
Montanez, who won the Double-A Eastern League's Triple Crown last season and then homered in his first big league at-bat, has hit .204 in just 48 at-bats this season. The Orioles originally envisioned him as an offensive alternative to left fielder Felix Pie, a role that has fallen to Nolan Reimold over the last few weeks.
The Orioles used Montanez as a reserve over the past few weeks, and he played despite having the injury. Montanez was told he couldn't do much more damage, but decided that now was the right time to fix his thumb.
"That was his decision, and I agreed," Trembley said. "He wanted to get it done as soon as he possibly could and get it out of the way. I said, 'Lou, if that's what you want to do, I'm in complete agreement with getting it done.' ... He wanted to get it done and start his rehab process. He told me he will probably end up playing winter ball."
Spencer Fordin is a reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.