PITTSBURGH -- Orthopedic surgeon Dr. Tim Kremchek examined Nationals third baseman Ryan Zimmerman's injured left shoulder in Cincinnati on Tuesday night and confirmed that Zimmerman has a small tear in the anterior labrum of his left shoulder and also has some mild rotator cuff weakness.

Zimmerman, who hasn't played since May 25, is expected to miss four to six more weeks. The third baseman will begin a rehab plan immediately, working his shoulder with a variety of exercises.

"Anytime you're not talking about surgery it's better," Acta said. "With that said at the end of the rehab if things don't work out, we'll probably go that route. But the doctor seemed to be very optimistic that that won't be necessary."

Zimmerman is expected to avoid baseball-related activities for the next month. After that time, he will pick up a bat and begin hitting again.

"He's going to do the rehab, and at the end of the rehab, the doctor is going to decide depending on how he feels," Acta said.

In other injury news, Nationals left-hander Matt Chico was examined by Dr. James Andrews in Birmingham, Ala., who confirmed that he has significant ossification of his ulnar collateral ligament and loose bodies in the back of his left throwing elbow. He recommended rest and rehab for the next six weeks.