Mena was optioned to Triple-A Reno on Sunday.
Diamondbacks GM Mike Hazen said in early February that Mena is "not a finished product" and was likely to begin the campaign at Triple-A, so this move was to be expected. The 21-year-old spent most of 2023 at Double-A Birmingham and had a 4.66 ERA and 1.35 WHIP over 114 innings, but he showcased his strikeout potential with a 10.7 K/9.