Koch has been with the Diamondbacks since they acquired him from the Mets in a 2015 trade centering on Addison Reed, but the former has since struggled in the majors. Dating back to his 2016 debut, Koch owns a 4.88 ERA/5.99 FIP with 4.95 K/9, 2.23 BB/9 and a 42.2 percent groundball rate in 125 1/3 innings (36 appearances, 16 starts). Koch got off to a brutal start over 20 frames this year prior to his designation, as he logged a 9.15 ERA with 3.92 K/9, which offset an impressive walk rate (1.74).
The 28-year-old Koch has also fallen flat at the Triple-A level, where he carries a 5.79 ERA with 5.0 K/9 and 2.0 BB/9 in 146 innings. And he’s out of minor league options, which further takes away appeal.