"Just a little stiffness, didn't feel right so I shut it down, got an MRI and it's perfectly fine," said Barrett, who has recently begun playing catch again.
The team said the MRI showed no structural damage.
"He's obviously a little bit behind," D-backs manager Torey Lovullo said. "He's in a throwing progression and as far as his ramp-up timing, we're not sure at this point in time, but we're going to take it day by day. Knowing that he's a reliever, getting him ramped up is not as big of a challenge for someone who is a starter. We feel like he could catch up, but the timeline is yet undetermined."
Steve Gilbert has covered the D-backs for MLB.com since 2001. Follow him on Twitter @SteveGilbertMLB. This story was not subject to the approval of Major League Baseball or its clubs.