Ryan Zimmerman didn't play for the Washington Nationals on Sunday, instead undergoing an MRI on his right shoulder.

Zimmerman has been unable to make a regular, comfortable throw to first base. The MRI revealed inflammation.

Matt Williams said the MRI showed no "structural issues" and that Zimmerman will be reevaluated after Monday's day off.

"The issue he's got is probably throwing overload," Williams said. "He throws a lot, and he works at it really hard, so it may be a little overload at this point."

Zimmerman is hitting .350/.333/.550 with a home run and three RBI in six games this season.