He received 11 stitches in his chin and jammed his shoulder, but didn't sustain a concussion after slamming into the wall in right field on Monday night.
Harper left the game in the fifth inning and the Nationals went on to beat the Los Angeles Dodgers 6-2 in the opener of a 10-game road trip. He didn't want to talk to reporters after the game.
Harper hit the scoreboard wall face-first while tracking a ball hit by A.J. Ellis over his left shoulder. He never looked at the wall and when he finally turned, he was on top of it. The impact sent Harper's cap flying as he bounced off the wall and crumpled to the ground, with Ellis getting a triple.
"As the ball kept going, I was like, 'Is he going to stop?'" Nationals center fielder Denard Span said. "He looked like he didn't get a good jump at all, like he was surprised the ball was hit to him. I thought he was going to jump and brace himself. As soon as he ran into it, his body locked up."
Harper rolled onto his back and lay there for a couple minutes.
"You could tell he didn't know where he was at," Span said. "He just kept asking me, 'Is it bad? Is it bad?'"
In the dugout, manager Davey Johnson briefly thought Harper might be unconscious.
Harper eventually got up under his own power. Streaks of blood from his chin that got cut on the chain link covering the scoreboard were evident on his neck as he walked off the field.
"It definitely wasn't pretty seeing the blood trickle down his neck," Span said. "He's a warrior. I guarantee you, he's probably going to try to play tomorrow."
Harper was playing just his second game after missing two with an ingrown toenail that required surgery.
He drew praise from other teammates for his willingness to go all-out.
"I thought it was a routine fly ball, but it kept carrying," winning pitcher Jordan Zimmermann said. "That's all you can ask for as a pitcher, a guy going 110 percent."
It wasn't Harper's first collision with the wall at Dodger Stadium. Last year in the second game of his career, he hit the center-field wall while making a catch and hurt his back.
On April 30 in Atlanta, he bruised his left side leaping toward the fence while trying to prevent a home run.
"I would rather him not go all-out into the wall," said Ryan Zimmerman, who drove in three runs. "Some people look at it as a bad thing. If you play that hard every day, there is something to be said about that. He's going to play a long time and you have to learn to take care of your body. As he grows, he'll learn what to do and what not to do."
Johnson said, "I don't want to change him."
Dodgers manager Don Mattingly described Harper's collision as "scary."
"That fencing we have is a little dangerous," he said. "If you hit that, you're going to feel it, especially face first."
Zimmermann (7-1) won his NL and major league-leading seventh game, allowing nine hits and two runs in 7 2/3 innings, striking out five and walking none.
"I've always been confident. I feel like I haven't changed anything from last year," he said. "I feel if I keep that up I'm going to have a lot more quality starts."
The Nationals ended a five-game skid at Dodger Stadium, where they were swept last year when Harper made his major league debut.
"This is where he broke in a year ago, so he was excited to be here," Johnson said about Harper.
"I threw about 10 pitches after that," Beckett said. "My groin hadn't been bothering me. I've don't think I've ever had groin problems."
Beckett (0-5) gave up four runs -- two earned -- and three hits in three innings while striking out five and walking two.
"The problem is that I'm just stinking. I'm in one of those ruts right now," he said. "It seems like if they hit the ball soft it's a hit, if they hit the ball solid, it's a hit. I have to figure out a way to get out of it."
Zimmerman's RBI grounder in the first gave Washington a 1-0 lead. His RBI double added two more runs in the third, when LaRoche made it 4-0 on an RBI groundout. Beckett gave up three runs on one hit in the inning.
The Nationals extended their lead to 6-0 in the fifth. Zimmerman grounded into a fielder's choice to pitcher Javy Guerra, and Steve Lombardozzi scored on Guerra's throwing error. LaRoche's RBI single scored Harper, who walked.
Nationals RF Jayson Werth, on the 15-day DL with a strained right hamstring, will see a doctor in New York on Tuesday. He's likely to rejoin the team this weekend in San Diego. ... Dodgers RHP Zack Greinke will pitch on Wednesday; the team just isn't sure whether it will be for them or at Single-A Rancho Cucamonga. He is on the 15-day DL with a broken left clavicle. ... Dodgers 1B Adrian Gonzalez returned after getting Sunday off, and extended his hitting streak to 10 games with a single in the first. ... The Nats improved to 16-2 when scoring first this season. ... The Nats opened a 10-game trip, tying their longest of the season.