The move Wednesday came four days after Texas designated Detwiler for assignment. He will be a free agent Friday if he clears waivers.
Detwiler started the season in the rotation after an offseason trade with Washington for two Texas prospects. The 29-year-old went 0-5 with a 6.95 ERA in seven starts and was sent to the bullpen after a stint on the disabled list with shoulder inflammation.
After 10 more appearances as a reliever, Detwiler's 7.12 ERA was highest in the majors among pitchers with at least 40 innings at the time Texas dumped him.