Rodriguez recently visited noted orthopedic surgeon Dr. James Andrews, who diagnosed Rodriguez with the injury. The lefty said that he feels the pain "in the bone" when he pitches.
The 34-year-old still hopes to return to the Pirates active roster despite the injury, possibly as a reliever. Rodriguez threw a bullpen session on Sunday, and hopes to rejoin the team later in the month.
Rodriguez expressed his frustration to Sanserino, telling the reporter:
"It's a hard situation for me. It's the first time I've been on the DL like that, for three months. Never in my career. I've missed like 15 days, but no more. I see how my team's playing right now, it's very hard."
The Pirates placed Rodriguez on the disabled list June 6. He had pitched well before being shut down, going 6-4 with a 3.59 ERA.
Pittsburgh acquired Rodriguez from the Houston Astros in July of 2012, sending three minor leaguers to Houston. Rodriguez holds a $13 million player option for 2014; the Pirates would pay $7.5 million of his salary next year if he exercises the option.