As Young was throwing to first, his right leg hit the sliding Harper in the head. Harper was down on the ground for several minutes as manager Matt Williams and head athletic trainer Lee Kuntz came to his aid.
Harper got up under his own power and remained in the game, collecting his first hit of the season during the Nationals' two-run seventh.
"I saw him sliding into second base, trying to wipe me out," Young said. "He just happened to hit my shin and dinged me up a little bit, but obviously, I hit him in the head. He was making a hard slide, taking me out and it was one of those ... wrong place wrong time [kind of things]."
Harper was twice given a full concussion test -- once right after the incident and another after the game -- and said he is fine.
"He is good. He had a concussion test from the doctor. He was cleared, he felt OK. He got banged, but he passed all the tests," Williams said.
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.