Koch won't make a spot start Saturday against the Nationals, as the Diamondbacks announced Anthony Banda would instead be recalled from Triple-A Reno to take the hill, Jarrid Denney of MLB.com reports.
Since Taijuan Walker was placed on the paternity list Thursday and isn't due to rejoin the Diamondbacks until Sunday, the Diamondbacks were in need for a spot starter Saturday, with Koch considered one of the leading candidates to fill the void. After being called up from Triple-A in a corresponding move for Walker's placement on the paternity list, Koch went unused out of the bullpen both Thursday and Friday, which would have left him available for Saturday. However, since the right-hander had compiled an 8.47 ERA over 17 innings with Reno, the Diamondbacks evidently weren't comfortable deploying Koch in the rotation on even a temporary basis, so it's likely that he'll head back to the minors Saturday to facilitate Banda's promotion to the big club.