The Orioles placed right-handed starter Chris Bassitt on the 15-day injured list, retroactive to Friday, with low back discomfort, and recalled right-hander Trey Gibson from Triple-A Norfolk on Monday.
Gibson will start tonight's game against the Mariners.
In his previous start on Wednesday against the Red Sox, Bassitt cruised through the first two innings on 20 pitches before laboring through the third and exiting his start early with a back injury, turning the ball over to Albert Suárez for the fourth in an 8-1 loss.
In his first season with Baltimore, the 37-year-old has a 5.27 ERA in 12 outings (10 starts).