Arizona designated Solomon for assignment Monday.
Solomon will lose his spot on the 40-man roster after the Diamondbacks needed to clear room for outfield prospect Kristian Robinson (hamstring), who was reinstated from the restricted list. Since being optioned to Triple-A Reno on May 3 following a month-long stay in the big leagues, Solomon posted a 9.31 ERA and 2.17 WHIP over 9.2 innings.