Harrison (biceps inflammation) on DL
Harrison, who had an MRI that showed no structural damage, said Saturday he has also been experiencing numbness in his left hand and is scheduled to visit a neurologist to rule out nerve damage.
Right-hander Tommy Hunter will be called up from to start in Harrison's place Sunday night against San Diego.
"I don't know what's going on," Harrison said. "I just don't feel like myself."
Harrison went on the disabled list May 26 with left shoulder inflammation and made two starts after he was activated June 17.
In a loss Tuesday to Arizona, Harrison allowed seven runs in 3 2/3 innings.
The 23-year-old said he didn't experience any discomfort during his last outing. He said he began to have problems after his start against the Diamondbacks.
The MRI came up clean Friday, and Harrison is scheduled to visit a neurologist July 6. Harrison said poor mechanics may be the cause for the ailments.
Rangers manager Ron Washington said the team doesn't want take any chances.
"We're going to put him on the DL and get everything well," Washington said.
Hunter made a spot start on May 29, giving up three runs in 5 1/3 innings against Oakland.
Harrison, who went 9-3 in 15 starts as a rookie in 2008, is 4-5 with a 6.11 ERA in 11 starts this season.
Copyright 2009 by The Associated Press