Buchanan is 2-7 with a 9.00 ERA in 10 starts this season.
The Phillies promoted left-hander Cesar Jimenez to take Buchanan's spot on the 25-man roster, solely to help an overworked bullpen. The Phils will need to fill Buchanan's spot in the rotation at some point, and one of the pitchers the club acquired in the Cole Hamels trade could be the choice.
Lehigh Valley right-hander Jerad Eickhoff is 2-0 with a 0.64 ERA in two starts since joining the organization. Righty Alec Asher is 1-0 with a 2.77 ERA in his first two starts for the IronPigs.
Todd Zolecki is a reporter for MLB.com. Read his Phillies blog The Zo Zone, follow him on Twitter and listen to his podcast. This story was not subject to the approval of Major League Baseball or its clubs.