The Brewers selected Boxberger's contract from their alternate site Tuesday.
Milwaukee created a spot for him on the 40-man roster and 26-man active roster, respectively, by transferring Justin Topa (elbow) to the 60-day injured list and trading Orlando Arcia to Atlanta. Boxberger appeared to have made a strong push for the Brewers' Opening Day roster coming out of spring training, but Milwaukee instead had him bide his time at the alternate site for a few days before a roster spot opened up. Though he has 77 career saves on his resume, Boxberger is expected to work in a middle-relief role for Milwaukee initially.