Miller, who was selected by the D-backs in the 11th round of the 2014 Draft out of Vanderbilt University, had a 2.93 ERA last season in 53 relief appearances for Double-A Jackson and Triple-A Reno.
While with Reno, Miller had a 1.72 ERA and limited opponents to a .147 batting average.
Miller was converted from starter to reliever prior to the 2016 season, and it was around that time that fellow Vanderbilt alum David Price helped him develop a cut fastball, which he picked up quickly and used it to thrive in relief.
Miller, who is the D-backs' 17th-best prospect according to MILBPipeline.