Activating Harper comes before the Nationals play the Philadelphia Phillies in the second game of a three-game series at Citizens Bank Park.
Harper was initially placed on the 10-day disabled list Aug. 13 after he suffered what the team termed a "significant bone bruise" in his left knee after he slipped on first base trying to beat out a throw against the San Francisco Giants. He was also diagnosed with a left calf strain.
Now healthy, Harper should return to his familiar post in right field and continue to operate as a tone-setter for the Nationals at the plate and on the field as Washington eyes its first trip to the World Series.
Prior to hitting the shelf, the 2015 National League MVP slashed .326/.419/.614 with 29 home runs, 87 RBI and a league-high 1.034 OPS.
As those numbers indicate, Harper is the kind of singular talent whose production can propel the Nationals to new postseason heights.
And considering Washington has been dispatched from the playoffs in the division series each of its past three trips, the pressure will be on Harper and the Nationals to exorcise their demons once and for all.
By being activated now, the Nationals ensure Harper will be able to get at-bats over their final six regular-season games with the hope he's back at full strength when the National League Division Series begins on Oct. 6.