The Rangers optioned right-handed reliever Nate Adcock to Round Rock to make room for Ross. Adcock had a 4.50 ERA in seven appearances for the Rangers while opponents were hitting .289 off him.
"It gives us another left-hander and it gives Adcock a chance to work on his mechanics," Rangers manager Ron Washington said. "Now [Claudio] gets a chance to get big league hitters out."
Claudio, who was called up Wednesday when Yu Darvish went on the disabled list, joins Neal Cotts as the Rangers' two left-handed relievers. Cotts is a free agent after the season, although the Rangers have indicated they would like to re-sign him. The Rangers still have left-handed relievers Aaron Poreda, Michael Kirkman and Ryan Feierabend at Triple-A.
Ross was a left-handed setup reliever the past two seasons before moving into the rotation this year. He could be switched back to the bullpen next year.
"That's to be determined," Washington said.
But the Rangers know that good left-handed relievers are a premium at the Major League level, and that's why they want to take a look at Claudio.
"His name was on the list, whether it was this year, Spring Training or next year," Washington said. "We didn't know when, we just needed a pitcher now."
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.