"It isn't good that he couldn't throw on his fifth day," D-backs manager Chip Hale said. "Hopefully everything will be OK, but it's concerning."
Forearm and elbow tightness can be a precursor to issues with the ulnar collateral ligament. De La Rosa has already had Tommy John surgery to repair the ligament in August 2011.
• Outfielder A.J. Pollock (fractured elbow) is expected to remain with Class A Advanced Visalia until Thursday and then move to Triple-A Reno to continue his rehab assignment.
• Shortstop Nick Ahmed received an anti-inflammatory shot in his ailing hip. Hale said he still expected that Ahmed will return before the end of the regular season.
• Left-hander Andrew Chafin (shoulder tendinitis) could be activated Monday when the team returns from this road trip.
• Catcher Chris Herrmann (strained left hamstring) is expected to begin a rehab assignment Monday.
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.