Stephenson was placed on the 10-day injured list Tuesday with a back strain.
Stephenson had a rough outing in his first relief appearance of the season, giving up two runs on two hits and no walks while recording one strikeout as the only out he logged. However, the injury may have had something to do with his struggles, and he'll be sidelined for a minimum of 10 days. It's unclear exactly how much time he'll miss.