Stephenson (shoulder) was transferred to the 60-day injured list Monday.
The Reds have not announced how long Stephenson will be sidelined with his broken clavicle, but Monday's transaction rules him at least until Sept. 21 and indicates his injury could be a season-ender. The Reds figure to mix-and-match behind the plate until either Stephenson is ready to return or the regular season comes to a close.