"He went to his backhand tonight, threw that ball across the infield and felt pain in his shoulder, so we thought it prudent to get him out of there and make sure everything is OK," Williams said.
Zimmerman underwent surgery on the shoulder in October 2012 after having trouble with it throughout that season, receiving multiple cortisone shots to manage the inflammation. He returned last season and played in 147 games, but the shoulder continued to be an issue as he committed 16 throwing errors.
Zimmerman dealt with some mild soreness during Spring Training, but Williams said his third baseman had felt fine until his error on Saturday. On that play, he backed up to field a hard grounder, then looked uncomfortable as he sailed the throw well high and wide of first baseman Adam LaRoche.
"He was fine [before that]," Williams said. "But again, it's cold out there. In between innings, you don't necessarily get all the way loose, either, with the weather. He felt it, so we're just making sure."
Another setback with the shoulder would be a tough blow for Zimmerman and his teammates, who have watched him work to overcome the problems over the past few seasons.
"It's hard for all of us, as it is for him," LaRoche said of Zimmerman's situation. "He's our captain on this team, and he's a big piece of it, to say the least. So to watch him go through that, it's frustrating, and we're all behind him, and we'll do whatever we can to help him out. I know it's eating at him, and that's a guy that's in that cage when nobody's around, throwing all day long. Nobody wants it worse than he does, and he's putting the time in and trying to find it, so he'll be all right."
Andrew Simon is a reporter for MLB.com. Follow him on Twitter @AndrewSimonMLB. This story was not subject to the approval of Major League Baseball or its clubs.