Mullins was unavailable for Friday's game against the Tigers due to neck discomfort, Andy Kostka of TheBaltimoreBanner.com reports.
The 29-year-old's neck issue stems from his collision with Austin Slater during Thursday's contest. The Orioles haven't offered any information regarding the severity of Mullins' injury, but he can be considered day-to-day for now. Slater, Colton Cowser and Anthony Santander started across Baltimore's outfield Friday, and the O's would likely roll out the same trio if Mullins is unable to play Saturday.