The Nationals announced Harper suffered a right hamstring strain and will be re-evaluated Friday. Harper was injured rounding second base in front of a double by Archie Gilbert. Harper was replaced by outfielder Chris Rahl. Harrisburg won the game 4-2 over the Aeros.
Harper went 1-for-3 in the game and had walked to lead off the frame. He is batting .254 in 36 games at Double-A with three homers and 12 RBIs. He is batting .297 with 17 homers and 58 RBIs in 108 games between Single-A Hagerstown and the Senators.
The Nationals could decide to shut Harper down for the season if they deem the injury to be serious. The Senators have 18 games remaining on the regular season schedule. Harrisburg is also in a dogfight in the western division for a playoff berth, leading Bowie by two games at 70-54.
The 2011 Arizona Fall League opening game for the Scottsdale Scorpions is Oct. 4. If the Nationals want Harper to play for Scottsdale again, that would give him at least 45 days before that game.