McCarthy, at Triple-A Oklahoma City after not making the Rangers' rotation out of spring training, has been put on the seven-day disabled list in the minor leagues after feeling soreness in his right shoulder after his last start.
The right-hander was 7-4 with a 4.62 ERA last season, when he was limited to 17 starts because of a stress fracture in his right throwing shoulder. He had the same problem in 2007.
Rangers physician Dr. Keith Meister determined that there is a recurrence of the stress fracture and recommended rest.
McCarthy is 1-0 with a 2.51 ERA in four starts for Oklahoma City.