Warren was designated for assignment by the Rangers on Saturday.
Warren was claimed off waivers by the Rangers in October, but he'll now be removed from the 40-man roster after the team signed right-hander Kohei Arihara in a corresponding move. Warren spent the entire 2020 season at the Mariners' alternate training site but made six relief appearances in 2019, tossing 5.1 scoreless innings with a 5:2 K:BB during that time.