Miller was added to the Diamondbacks' 40-man roster Monday to protect him from the Rule 5 draft.
Miller appeared in 31 games at Double-A Jackson and 22 at Triple-A Reno during the 2017 season. Between the two he combined to pitch 70.2 innings and posted a 2.93 ERA and 1.09 WHIP. Miller could earn a chance to pitch in the big club's bullpen during the 2018 campaign should he continue his solid performance.