Harper said he had no idea that he hit his 100th double until after the game when he saw the ball by his locker.
"Definitely a great accomplishment, but on to the next one hopefully," Harper said. "I'm just trying to build on what I'm doing and get better."
Harper, who also needs one more home run to reach the 100th of his career, is off to a good start, going 5-for-13 (.385) with two home runs, three RBIs and a .556 on-base percentage.
"I'm just trying to have good at-bats -- to see pitches and get pitches in my zone that I can drive," Harper said. "I'm just trying to have that right approach up there, wait for my pitch and drive that pitch. I'm just trying to take it day by day, at-bat by at-bat."
Bill Ladson is a reporter for MLB.com and writes an MLBlog, All Nats All the Time. He also can be found on Twitter @WashingNats. This story was not subject to the approval of Major League Baseball or its clubs.