Teammates congratulate Bryce Harper after he hit a three-run home run during the seventh inning in Washington’s win Sunday against San Diego. (Denis Poroy/Getty Images)

Days like Sunday are what make the Washington Nationals such a captivating team, when the talented roster many believed would contend for a title in 2015 is on full display.

In a 10-5 victory over the San Diego Padres, Bryce Harper’s torrid hitting showed no sign of ending. And Stephen Strasburg, the Nationals’ other first overall pick, mired in a career-worst slump, regained some of his confidence on the mound.

Harper smashed a triple to start the Nationals’ critical rally in the fifth inning, in which they grabbed command of the game. He added a run-scoring single in another offensive outburst in the sixth. And as the Padres limped around, Harper clobbered a stunning three-run home run to left field in the seventh. Only 39 games into the season, he leads the National League in home runs (14), runs (36), RBI (37), walks (36) and on-base-plus-slugging percentage (1.206).

“It’s to our lineup,” Harper said. “Having [Yunel] Escobar in front of me and [Ryan Zimmerman] behind me. Being able to go about my business every single day the right way and staying in the lineup. That’s what I want to do. I’m staying in the lineup. I want to have some fun.”

Meanwhile, Strasburg, pitching in his home town for only the second time, fired five-plus solid innings, looking more in control and at ease than he has in weeks. He allowed three runs in leading the Nationals to their 15th win in 19 games, but his fastball command was improved. He struck out seven, adopting the advice the Nationals gave him before the start.

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“It’s progress,” Strasburg said. “Gotta just keep plugging along.”

Five days ago, in a 14-6 loss to the Arizona Diamondbacks, Strasburg relied too much on his secondary pitches and not the hard fastball. The Nationals gave him a simple message. “Be aggressive with your pitches and go after them,” Manager Matt Williams said. “He’s got really great stuff.”

From the start of the game Sunday, Strasburg’s game plan was obvious. He finished with 64 fastballs in 91 pitches, his highest use of the pitch in a start this season.

“The way he threw today, that’s the way he is,” catcher Jose Lobaton said. “That’s something positive for him that we win the game so for the next start he’s going to be more relaxed.”

Strasburg struck out three in the first inning. His second strikeout came on a wild pitch, allowing Abraham Almonte to reach base. Almonte then stole second base. He broke for third when Matt Kemp hit a ball up the middle that second baseman Danny Espinosa dived for and stopped. But Espinosa threw home and Almonte beat it.

Strasburg gave up a solo home run to Justin Upton in the third inning, which put the Nationals in a 2-0 hole that they would overcome thanks to Harper and Espinosa. After Harper tripled off Padres starter Ian Kennedy to start the fifth inning, the Nationals’ first hit, he pumped his fist in excitement at the Nationals’ dugout.

“I just wanted to get everybody going,” Harper said.

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Zimmerman reached on an infield single to put runners on the corners with no outs. But Tyler Moore and Lobaton popped out to bring Espinosa with two outs. Espinosa clobbered a three-run home run to right field that put the Nationals up 3-2, his much improved left-handed swing one of the most encouraging developments of the Nationals’ season.

“Just get a good pitch to hit,” Espinosa said he told himself at the plate. “Trying to look for something on the plate I can drive. Got a little over aggressive on the first pitch. Told myself to be patient.”

With a lead, Strasburg fired a scoreless bottom of the fifth. The Nationals again boosted Strasburg with a scoring binge. They chased Kennedy from the game in the sixth and put the score out of reach with a four-run rally. After two reached against Strasburg in the sixth, Williams replaced him with Tanner Roark, allowing Strasburg to leave the game with a good feeling.

After the win — which moved Washington a season-high five games over .500 — Strasburg said he was pleased with the improvement of his fastball, his change-ups to left-handed batters and his curveball, which got six swings-and-misses.

“I just wanted to go out there today and keep the team in the ballgame and give us an opportunity to win, and they went out there and did it,” Strasburg said.

With the Nationals ahead 7-3, Harper took over again. Ian Desmond and Escobar both singled with one out against Dale Thayer. Thayer tried to get Harper to chase pitches high and outside. Harper swung at and missed the first one, fouled off two and took one. Thayer threw a 92-mph fastball on the high outer corner of the strike zone. Harper sent the ball into the left field seats, his 14th homer of the season.

“Right now, he’s seeing the ball so well that there’s no weakness,” Padres Manager Bud Black said. “You try to get to a spot, and if you get there he seems to take it or foul it off. He’s really, really swinging the bat well.”

Harper got a chance to hit for the cycle in the ninth, but he grounded out to end the inning. It was the only time Harper didn’t reach base Sunday.

“Oh my god,” Lobaton said. “I’m gonna say O.M.G. He’s unbelievable. . . . People are gonna get scared. The way he’s seeing the ball, he’s hitting everything.”