Gallen (elbow) will return from the injured list and start Wednesday's game against the Royals, Jody Jackson of DBacks.tv reports.
Wednesday will mark Gallen's first appearance of the second half, as the 31-year-old has been on the shelf since July 12 due to right elbow inflammation. He pitched 1.2 scoreless innings in a rehab game at Triple-A Reno on Aug. 30 before building up to four innings during a sim game Friday. Rather than waiting for him to build his workload further, the D-backs will have him make what will likely be an abbreviated start Wednesday before turning the game over to Michael Soroka (shoulder), who will also be activated prior to the series finale.