Boggs, who served as the setup reliever for closer Jason Motte during the 2012 season, has struggled this season. He assumed the closer spot when Motte was lost for the season with an elbow injury and blew three save opportunities.
His latest came Thursday when he allowed two runs in the ninth without recording an out in a 4-2 loss to Kansas City. Boggs has an 11.05 ERA in 14 2-3 innings. This marks the second time he's been demoted this season.
Butler made 13 appearances at Double-A Springfield (Mo.), giving up one run in 13 2-3 innings. He's struck out 21 and walked two, and had a 0.66 ERA.