The Nationals transferred Poulin (forearm) from the 15-day injured list to the 60-day IL on Sunday.
Poulin had been on the shelf since July 19 due to a left flexor strain, and his move to the 60-day IL ensures that he'll remain out through Sept. 13. The southpaw's move to the 60-day frees up a spot on the 40-man roster for one of Yovanny Cruz and Jake Bird, two of the four players the Nationals acquired Sunday in the deal that sent Luis Garcia to the Yankees.