To clear a roster spot, the Orioles optioned reliever Donnie Hart to Triple-A Norfolk, keeping their four-man bench and potentially shortening up the 'pen down the road.
"With Chris [Tillman], it's kind of six starters [on the roster]," Orioles manager Buck Showalter said of the decision to option Hart. "We've gotten some good starts, it's kind of where it fell. We are what, 2 1/2, three weeks from September [roster expansions]?"
Hart, 29, pitched a scoreless inning of relief Tuesday, but he had allowed runs in his two previous outings. He has a 3.12 ERA in 39 games for the Orioles this season.
Trumbo, who was inserted back into the designated hitter spot Wednesday, is batting 238/.300/.405 in his second year with the O's. He is coming off a stellar 2016, in which he hit a Major League-best 47 homers along with a career-high 108 RBIs. Baltimore signed him to a three-year, $37.5 million deal this offseason.
The Orioles were hoping to add infielder Ryan Flaherty for their next series in Oakland, but Flaherty (right shoulder) still has some roads to cross on his rehab assignment.
Brittany Ghiroli has covered the Orioles for MLB.com since 2010. Follow her on Facebook and Twitter @britt_ghiroli, and listen to her podcast. This story was not subject to the approval of Major League Baseball or its clubs.