Buckner, 26, is slated to start Tuesday's game against the Marlins.
The right-hander, who pitched with Arizona in 2008 and '09, was sent to the Minors after Spring Training and made seven starts for Reno. He served in that role effectively for the Aces, compiling a 3-1 record to go with a 3.53 ERA. Buckner had also thrown five consecutive quality starts, going 3-0 with a 1.93 ERA over that stretch.
Boyer had worked exclusively out of the bullpen for the D-backs and had been struggling. The 28-year-old right-hander posted a 1-2 record with a 7.82 ERA in 14 relief appearances. He has 182 games at the Major League level and holds a career 4.97 ERA over stints in Atlanta, St. Louis and Arizona.
Bailey Stephens is a reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.