Zimmerman has had a frustrating first half, hitting .221 with 12 home runs and 38 RBIs. It seemed like he may have been getting his swing together against the Brewers on Wednesday afternoon, when Zimmerman went 2-for-3 with a home run and two RBIs.
"He felt sore on the swing yesterday, so he is day to day. We will evaluate tomorrow," Baker said. "It's real tough. It's real tough. It felt like he was getting going. We have to deal with it -- it is what it is."
With Zimmerman out, the Nationals are short on the bench. Clint Robinson started at first base, and that means the Nationals only have three players available on the bench for Thursday's game. Baker indicated that the Nationals may have to call up a position player from Triple-A Syracuse before Friday's game against the Mets.
Bill Ladson has covered the Nationals/Expos for MLB.com since 2002 and writes an MLBlog, All Nats All the Time. He also can be found on Twitter @WashingNats. This story was not subject to the approval of Major League Baseball or its clubs.