Harper said after the game on Saturday that if he didn't feel right Sunday, then he wouldn't play. His exit from the game was a precautionary move, according to Nationals manager Matt Williams.
Washington will surely miss Harper's bat in the lineup. He leads the Major Leagues in walks (52), on-base percentage (.479), slugging percentage (.725) and OPS (1.204). Harper has also reached base safely in 32 of his 33 road games.
Clint Robinson, who started at first base in the first two games of the series and hit his first career home run on Thursday, will take Harper's spot in right field against the Brewers.