Koch was assigned to Triple-A Columbus on Sunday.
Koch last pitched in 2019 with the Diamondbacks, where he had a 9.15 ERA and 1.60 WHIP across 20.2 innings. He also saw time with Triple-A Reno, but posted an underwhelming 7.38 ERA and 1.65 WHIP in 100 innings, mainly as a starter, in the minors. Koch is unlikely to play much of a role in the majors in 2021.