Washington Nationals right fielder Bryce Harper left Wednesday's game at Atlanta in the sixth inning due to a side muscle injury.
The reigning National League Rookie of the Year tweaked his left side on a checked swing to start the inning.
Harper grounded out to finish the at-bat, but he subsequently left the game.
The injury related back to a bruise Harper received in the same spot while hitting the outfield wall Tuesday while unsuccessfully attempting to rob Braves pitcher Tim Hudson of a home run.
Harper hopes to return to the lineup Thursday for the series finale at Turner Field.
The Nationals won 2-0 Wednesday, ending a three-game losing streak.