Horn (elbow) will begin a rehab assignment Tuesday at Single-A Lakeland, Chris McCosky of The Detroit News reports.
Horn missed the entirety of spring training while working his way back from an elbow procedure he underwent in the offseason, so he'll likely require an extended stay in the minors before coming off the injured list. Once healthy, the 28-year-old may take a middle-relief role with the big club after posting a 1.59 ERA over 11.1 frames with the Tigers last season.