Arizona Diamondbacks right-hander Zac Gallen was removed from his start against the San Diego Padres in Mexico City after just three scoreless innings on Saturday after he was struck by a comebacker during the third frame. In his place, right-hander Brandon Pfaadt will take over. This will be Pfaadt's second relief appearance since transitioning to a bullpen role. His first effort was a 6.1-inning, one-run affair. Pfaadt threw a scoreless fourth inning immediately upon entering. The Diamondbacks led 4-0 after a two-run double by Jose Fernandez and a two-run homer by Alek Thomas Of course, the concern is now for Gallen's health. The Diamondbacks have since announced that it is a right shoulder contusion for Gallen. A contusion is, in essence, a bruise, of varying severity. This initial diagnosis could mean Arizona has avoided potential disaster, but it is still unknown whether or not Gallen will require further testing. A more severe issue is still within possibility, for the time being.…