"He is taking some medication to calm it down," Johnson said. "It's just normal. Nothing Earth-shattering."
Zimmerman has had shoulder problems dating back to last year and had surgery to fix the AC joint inside the shoulder after the season ended.
Zimmerman said recently he expects the shoulder to be in rehab mode for the rest of the season, but it will not keep him out of the lineup. Zimmerman's surgery on the joint was much more serious than anyone expected. That's why he is having problems throwing the baseball.
Zimmerman was not available for comment before the game against Arizona.
Bill Ladson is a reporter for MLB.com and writes an MLBlog, All Nats All the time. He also could be found on Twitter @WashingNats. This story was not subject to the approval of Major League Baseball or its clubs.