Irwin was the Pirates' 21st-round pick in the 2009 First-Year Player Draft and rising through their system until missing almost all of last season because of a nerve injury in his right elbow that required transposition surgery. Irwin, who made one start for the Pirates in 2013, was 1-2 with an 8.72 ERA in 10 games at Triple-A Indianapolis.
"He has been 89 to 92 miles per hour with his sinker and he has always had a good curve ball," said Josh Boyd, the Rangers' director of professional scouting.
T.R. Sullivan is a reporter for MLB.com Read his blog, Postcards from Elysian Fields and follow him on Twitter @Sullivan_Ranger. This story was not subject to the approval of Major League Baseball or its clubs.