Bryce Harper (0 for 5, three strikeouts) encounters a throng of autograph hounds in Cincinnati as the Nats’ rookie plays his third road series as a major leaguer. (Joe Robbins/Getty Images)

Bryce Harper sheepishly emerged from the trainers’ room in the Washington Nationals’ clubhouse late Friday night, a golf ball-size welt and 10 stitches over his left eye, clumps of blood in his hair and a new nickname from his teammates. After Harper had suffered a bizarre, frustration-fueled, self-inflicted injury, they fondly called him “Bam Bam.”

After the Nationals’ 7-3 victory over the Cincinnati Reds at Great American Ball Park, attention shifted from their encouraging offensive performance to how blood came to streak down Harper’s face as he stood in right field in the late innings. Rather than two-run homers by Danny Espinosa and Roger Bernadina, talk centered on how Harper had been sliced open releasing frustration during his worst game as a major leaguer.

Harper went 0 for 5 with three strikeouts. In his fourth at-bat, in the seventh inning, he grounded out to second base off Reds reliever Jose Arredondo. Back in the dugout, Harper took his bat down the tunnel that leads to the clubhouse and took out his frustration with a fierce swing against the wall.

Baseball players release anger in the same manner on ballfields every day, at every level, but it rarely goes so wrong. The bat bounced off the wall and drilled Harper above his left eye, immediately drawing copious blood.

“I just got caught up in the moment,” Harper said. “I want to do so well. It just got me.”

Manager Davey Johnson said Harper could miss one or two games, but Harper insisted he wanted to play.

“I think I’m good,” Harper said. “The doctor said I could play, so I’m going to play.”

After Harper smacked himself in the head, he shook it off and returned to the field for the bottom of the seventh, blood streaking down the left side of his face.

“Stitched it up as fast as I can and go back out to the outfield,” Harper said.

No teammates asked what happened, because they knew, either from the sound or from personal experience, what had happened.

“I didn’t think much about it,” Johnson said. “We put a band-aid on it, one of those butterflies. That’s what ballplayers do — break bats, throw helmets. That’s not anything new.”

Johnson had few qualms with Harper’s actions, mainly chagrin at his misfortune. “It’s an easy way to get rid of your frustration,” Johnson said. “I’ll speak to him about it, because evidently he went a little overboard. That’s not what you want to do. The equipment is supposed to take the brunt of it. We’ll address that.”

Harper took one more at-bat, striking out in the ninth inning. He said he would be more careful in the future.

“I guess I won’t do it anymore, but I don’t know,” Harper said. “I’ve done it a million times. It’s just a heat-of-the-moment kind of thing. It came back and got me.”

The strange injury overshadowed an uplifting victory. The Nationals arrived here in first place, with the most dominating pitching staff in baseball, but they still had problems to solve. The identity of their left fielder waffled on a daily basis. They needed Espinosa to break his season-long funk and replace some of the slugging the Nationals lost to injury. Their offense rarely showed up before the latter innings.

The game, then, supplied a bounty of happy developments. They scored three runs in the first inning — matching their first-inning total from all season — and seven in the first four. Bernadina, playing left, drilled a two-run homer and drove in three runs. Espinosa blasted a two-run home run a day after he declined a day off from Johnson.

Even if Gio Gonzalez lasted only five innings, the Nationals (20-12) could breathe easy for most of the game. Craig Stammen and Ryan Mattheus combined to load the bases with one out in the eighth inning, but Mattheus wiggled out of the jam without any damage, inducing a popup and then whiffing Zack Cozart.

Adam LaRoche provided another packed box score, going 2 for 4 with a walk and a double. In his last 11 games, he is 16 for 39 with four doubles, four homers and eight walks.

From the first inning, the Nationals pummeled Reds starter Mike Leake. Ian Desmond ripped the fourth pitch of the game into center field for a single, bringing Bernadina to the plate with an opportunity to assert control of the game for the Nationals and to convince his team that this year he will prove himself as a major leaguer.

Bernadina went ahead 3-1 in the count. He spit on a sinker he didn’t like, running the count full. And then he dug in. Bernadina fouled away four consecutive pitches. Leake threw a low, 90-mph sinker and Bernadina hammered it with a compact swing. The ball rocketed into the right field seats, giving the Nationals a 2-0 lead.

“I definitely have some more confidence out there,” he said. “I feel better.”

Bernadina came to the plate again in the second inning and flicked a single to right field, scoring Wilson Ramos from second for his third RBI in the first two innings. For good measure, he also stole second base.

Johnson has stuck by Espinosa, even if he entered Friday leading the NL in strikeouts while carrying a .191 average and Johnson had Steve Lombardozzi on the bench. With one out in the fourth inning and LaRoche on first, Espinosa delivered. He roped a laser into the right field seats off reliever Alfredo Simon, giving the Nationals a 6-0 lead.

“My swing felt good tonight,” Espinosa said. “Yesterday and today, I felt good. I was kind of searching for it a little bit. I have an idea of what they’re going to do. If I get a pitch in the zone I feel like I could handle, I’m going to take a shot. It’s definitely good to see a little bit of results.

“I knew I was going to figure it out and I wasn’t going to hit like this all year. I knew it was just a matter of time before I started locking in. I think that’s what I did tonight.

The Nationals would not look back. Afterward, they could all celebrate their victory. Harper, the 19-year-old they now called “Bam Bam,” had to find ice for his odd injury.

““It doesn’t hurt at all,” Harper said. “I feel fine. I didn’t get lightheaded at all or nothing. I feel good.”