Single-A Down East reinstated Acker (elbow) from its 60-day injured list Tuesday and assigned him to the rookie-level Arizona Complex League.
After undergoing Tommy John surgery last May, Acker opened the season on the IL before beginning a rehab assignment in the ACL on July 16. Though he's now been activated, Acker, who produced a 2.08 ERA and 0.92 WHIP in 13 innings over his five rehab appearances, will continue to build up with the Rangers' rookie-ball affiliate before potentially joining Down East before season's end.