Guerra's contract was selected by the Rays on Saturday.
Guerra pitched his way off the 40-man roster in mid-May but went unclaimed and remained in the Rays' organization. He owns a 6.75 ERA in 13.1 innings of relief at the big-league level this season, striking out nine batters while walking 18. His 5.94 ERA at the Triple-A level doesn't inspire confidence either. Elvin Rodriguez was designated for assignment in a corresponding move.