The Diamondbacks designated Beer for assignment Wednesday.
The transaction opens up a spot on the 40-man roster for right-hander Brandon Pfaadt, whose contract was selected from Triple-A Reno ahead of Wednesday's game against the Rangers. The 26-year-old Beer had yet to appear in the majors this season and slashed .200/.266/.314 in 79 plate appearances with Reno. His poor numbers at Triple-A and lack of defensive flexibility mean he's unlikely to be claimed off waivers.