Bryce Harper scores the go-ahead run in the ninth inning at Fenway Park. (Jim Rogash/Getty Images)

Bryce Harper favors action over stagnancy, the inclination of youth, and by late Sunday afternoon he could wait no longer. He had blown bubbles and watched for six innings, a foreign experience after 37 games in the major leagues. He marched down the tunnel and straight toward Manager Davey Johnson and told him he was fine. He then repeated himself: I’m fine.

“He made that point very clear,” Johnson said.

When they want something known, these Washington Nationals are unmistakable. Johnson inserted Harper two innings later, after the Nationals and Boston Red Sox had played to a draw for eight innings. In minutes, the 19-year-old flash of energy decided the outcome. Harper dashed around the bases on Roger Bernadina’s game-winning, two-out double in the ninth inning, giving the Nationals a 4-3 victory at Fenway Park to cap a resounding weekend.

The Nationals had swept the Red Sox, another statement for the emergent team with the second-best record in baseball. At 35-23, the Nationals stand 12 games over .500, their highest mark since July 23, 2005, and on a 97-win pace. They have widened their lead in the National League East to two games over second-place Atlanta and a staggering eight over last-place Philadelphia, the five-time reigning division champ. And they did at one of the most venerated parks, against of one the most high-profile teams.

“I know we’ve shown the baseball world what kind of team we are,” closer Tyler Clippard said. “This was kind of a statement series for us in doing that. They’re definitely a good club, and I think we’re better. I think we’re a lot better. We feel really good with what we’ve got going on right now.”

In another corner of the Nationals’ clubhouse, the statement-sweep notion did not sit well with second baseman Danny Espinosa. For him, their record means they don’t need to measure themselves against anyone; their opposition must measure themselves against the Nationals.

“I think we were the team to beat right here,” Espinosa said. “We’re the first-place team.”

The halcyon opening third of the Nationals’ season deepened the chasm between their present and past. The Nationals last came in here in 2006. They sent Livan Hernandez, Tony Armas and Shawn Hill to the mound, and the Red Sox outscored them by 17 runs. This weekend, they swept behind Stephen Strasburg, Gio Gonzalez and Jordan Zimmermann, who Sunday allowed three runs and struck out seven over seven innings. They are not what they used to be.

“There’s a lot of places I felt embarrassed,” said third baseman Ryan Zimmerman, the lone holdover from that team. “Not just here. That’s just the way it was. Now it’s a different story. We’ve got a long ways to go, still. I think a lot of things have changed.

The Nationals won Sunday despite their No. 2 through 5 hitters going a combined 0 for 15 with a walk and six strikeouts. They overcame the void with two doubles from Espinosa, who gave the Nationals a 3-2, seventh-inning lead in the seventh inning with a two-run double off the Green Monster. Clippard converted his toughest save yet, holding a one-run lead in the ninth by striking out Dustin Pedroia to end the game after allowing a one-out walk.

When the Nationals’ most needed a run, they turned to Harper. Johnson had held him out because coaches and trainers alerted him to stiffness in Harper’s lower back. Harper protested, but still sat. All game, he insisted he could play, and Johnson waited until the right moment.

“I’m pretty antsy when it comes to sitting,” Harper said. “I don’t like doing it. I like to get going and play.”

He pinch-hit for Tyler Moore in the ninth, with one out and the bases empty. When he saw catcher Jarrod Saltalamacchia meet Red Sox closer Alfredo Aceves on the mound, Harper thought, “He’s probably not going to give me anything.”

Aceves started him with three straight curveballs, only one of them of a strike, and that one barely over the inside corner. Harper spit on a low fastball and then took another fastball for ball four.

Up came Bernadina. He took a close ball, just off the inside corner, on 1-2. (Boston Manager Bobby Valentine would be ejected arguing balls and strikes on the game’s third-to-last pitch. “It was a ball,” Bernadina said.) On 2-2, Harper took off, a straight steal. Bernadina crushed it into right field.

“I was looking for his fastball,” Bernadina said. “He threw me one up, and I reacted.”

As the ball zipped past him, Harper thought, “I’m scoring.” The ball skipped into the corner. Third base coach Bo Porter anticipated sending Harper as soon as the ball left Bernadina’s bat. Right fielder Ryan Sweeney cut off the ball, but he had to leave his feet and slide to do so.

“That’s when I made up my mind,” Porter said. “I’m going to send him.”

Harper never hesitated, and his speed took over — Nationals coaches regularly time him running to first base in 3.96 seconds. As he rounded second, he locked his eyes on Porter, who windmilled him home. As Harper rounded third, his helmet nearly flew off his head. Adrian Gonzalez gathered Sweeney’s throw and fired it home. Harper slid in feet first, tapping the plate with his left hand. He hopped to his feet and pumped his fist.

For the run to matter, Espinosa had to land his pivotal blow. In the seventh, consecutive singles and a double steal by Ian Desmond and Moore put runners on second and third with no outs. But Jesus Flores whiffed and Bernadina popped up a bunt. The inning, packed with promise, fell to Espinosa.

Lester threw Espinosa a 2-1 cutter, and he launched the ball high to left field. Darnell McDonald drifted back, closer and closer to the Monster. Espinosa thought, “Ah, I didn’t get quite enough of it.” Desmond and Moore raced around the bases, certain runs depending on what happened to the ball falling out of the sky.

McDonald leapt. The ball thudded and rolled toward the infield. At 29 other ballparks, Espinosa’s drive would have been a deep but routine flyout. At Fenway, he rolled into second base with a double and the Nationals took a 3-2 lead.

“I’m pretty happy about that wall,” Espinosa said.

Zimmermann gave up the lead in the bottom of the seventh, but that only set up Bernadina’s laser and Harper’s dash. From the dugout, Johnson watched his young team embrace Harper as he walked into the dugout.

“It was picture perfect,” Johnson said. “Storybook perfect.”