Stites, 24, has yet to appear in a game this spring. He had an elbow issue before the start of camp, and an MRI taken in March showed inflammation, but no damage. He said Tuesday that there is no concern that the injury has gotten worse.
It seemed unlikely even before this latest setback that Stites would be ready in time for Opening Day on April 6.
Stites recorded a 5.73 ERA over 37 appearances out of the D-backs' bullpen last season, but his ERA over parts of four seasons in the Minors is 1.76.
Steve Gilbert is a reporter for MLB.com. Read his blog, Inside the D-backs, and follow him on Twitter @SteveGilbertMLB. This story was not subject to the approval of Major League Baseball or its clubs.