The Diamondbacks recalled Koch from Triple-A Reno on Thursday.
The right-hander accrued a 2.00 ERA in 18 major-league innings last year but has an 8.47 figure in 17 Reno frames. Koch will occupy a depth role among Diamondbacks relievers and may head back to the minors when Taijuan Walker returns from the paternity list, likely in the next few days.