Diekman, a 30th-round pick by the Phillies in the 2007 Draft, has pitched in 217 games in the Major Leagues over the past four seasons, posting a 9-11 record with a 3.65 ERA. He will enter the 2016 season with Sam Freeman as the Rangers' two primary left-handed setup relievers.
T.R. Sullivan is a reporter for MLB.com. Read his blog, Postcards from Elysian Fields, follow him on Twitter @Sullivan_Ranger and listen to his podcast. This story was not subject to the approval of Major League Baseball or its clubs.