Gallen has been scratched from Sunday's start against the Dodgers due to right elbow inflammation, Nick Piecoro of The Arizona Republic reports.
The injury may have cropped up following Gallen's last start Tuesday against the Padres, when he took the loss after allowing four runs on six hits and three walks while striking out five over six innings. The veteran right-hander is expected to go on the 15-day injured list, and he'll undergo further tests to determine the severity of the injury and establish a recovery timeline. Mitch Bratt is expected to replace Gallen as the Diamondbacks' starter for Sunday's series finale.