The Diamondbacks designated Frias for assignment Thursday.
Just two days after being optioned to Triple-A upon coming off the injured list, Frias will now lose his spot on the 40-man roster to make room for Andrew Knizner, who was claimed off waivers from Texas on Thursday. Frias has given up seven earned runs over 6.1 innings in the big leagues this season and owns a 4.88 ERA and 1.46 WHIP through 24 frames with Reno.