Harper was replaced Wednesday by Tyler Moore after his thigh bothered him during batting practice.
''I decided to get him out of there, give him a day just to calm it down a little bit,'' manager Matt Williams said. ''I expect him to be in there Thursday.''
The Nationals open an 11-game homestand Thursday when they play St. Louis.
Harper had been playing despite the ailment since last Friday, and he left Monday's game in the seventh inning after he slipped running the bases. He has been on a tear at the plate lately, batting .483 over the past eight games.