Swarzak, 35, has pitched for both the D-backs and Royals this season but been clobbered for 13 runs on 20 hits, including four homers, in 12 1/3 innings of work.
Davis has struggled to an 8.06 ERA over 25 2/3 innings out of the K.C. bullpen, surrendering an ungainly seven home runs over that limited sample size.