The Rays placed Duffy (hamstring) on the 10-day injured list Wednesday.
The transaction was merely a formality as the Rays finalized their active roster ahead of Thursday's season opener versus the Astros. Duffy remains in the midst of a two-week shutdown period, which the Rays hope will be sufficient maintenance time as he looks to overcome the strained left hamstring that has troubled him off and on during the spring. An exact timeline for his return from the IL probably won't be established until he's able to play in simulated or minor-league rehab games.