The move made room for the team to select David Holmberg from Double-A Mobile in time for the left-hander to start Tuesday night's game against the San Diego Padres.
Kubel, in his ninth major league season, was struggling at the plate and had seen his role limited mostly to pinch hitting. The31-year-old left-handed batter was hitting .220 with five home runs and 32 RBIs.
Kubel was signed as a free agent in December 2011 and got off to a strong start last season before tailing off in the late stages. Still, he hit .253 with a career-high 30 home runs and 90 RBIs.
The 22-year-old Holmberg was 5-7 with a 2.66 ERA in 25 starts for Mobile.