 Prior to the 2006 season, "MLB.com" beat reporter T. R. Sullivan opined that Feldman was the Rangers' top minor league relief prospect.In 2006, in 23 relief appearances for the Rangers' Triple-A affiliate, the Oklahoma RedHawks, he had a 1.98 ERA, and in 2007 in 21 relief appearances for the team he had a 4.50 ERA.Later in 2007, he pitched in the Arizona Fall League, to work on a new three-quarters delivery.