"In the triceps there's likeliness to get more fatigue there, especially if there's a long gap between innings," Darvish told reporters after his rehab start. "That's when I feel fatigue there. Not necessarily pain, but I can't for sure say there is nothing going on in the tricep zone."
Darvish has not pitched for the Cubs since May 20 but did throw five solid innings for Class A South Bend on Monday night.