More than any other pitch, Drew Storen’s slider makes him one of the best young closers in baseball. It’s what made him the 10th choice of the 2009 draft, one of the many young players trying to change the Nationals’ course. He feels more proud of a well-placed sinker than a sharp slider, because Storen expects greatness out of the slider. So Storen did not really need an assist improving his slider. But he got one anyway.

At Coors Field last Sunday, Storen saved two games, including one Sunday that required him to face the Rockies’ 2-3-4 hitters in a one-run game. The high altitude in Colorado makes the ball move less and often forces pitchers to abandon their breaking balls. Storen had a different solution. He just tried to throw his slider better.

“You really had to concentrate on trying to throw it the right way to make it move at all there,” Storen said.

Friday night, in the Nationals’ 4-2 win, the Phillies were the victims of Storen’s mini-lesson. After Storen got into a two-on, none out jam with Philadelphia’s 4-5-6 hitters coming to the plate in the ninth, he relied on his slider and unleashed some of the best ones he has thrown in the majors. They darted, at 84 miles per hour, like a car that had suddenly blown a tire.

With two on and none out, the most crucial hitter of Storen’s night came to the plate in the hulking form of Ryan Howard. Storen blew a 96-mph sinker past him for strike two, making the count 1-2. He nodded when Wilson Ramos called a slider. He threw it high in the zone and over the plate, confident it would bite sharply down and in. Howard took a wicked hack, but the ball had disappeared when he swung. The ball took a left turn, diving down and in.

“If that catches any of the plate, we’re having a different interview,” Storen said. “I saw where it started. You just know, ‘That better move.’ And it did.”

Storen’s filthy sliders and the save did more than just beat the Phillies, the Nationals’ third straight win over Philadelphia dating back to their series in June. His performance capped a milestone night for the Nationals’ rebuilding process.

In Potomac, Stephen Strasburg struck out five batters and walked none in 33 pitches, causing Spin Williams, the Nationals pitching coordinating, to declare him “in midseason form.” In Harrisburg, Bryce Harper blasted a walk-off home run over the batter’s eye in center field, then circled the bases with the joy and charisma that might make him the kind of player who sells jerseys not only in Washington, but Dubuque and Gainesville and Bangor and wherever. Strasburg provides cold-blooded legitimacy. Harper can take the Nationals national.

In Philadelphia, Danny Espinosa, 24, made three or four plays an average second baseman may not have. Wilson Ramos, 24, drilled a single off Cole Hamels and scored a run. Ian Desmond, 25, ripped a double and scored a run. Ryan Zimmerman, 26, walked twice, which helped end his hitting streak at 19 games. And Storen, who turned 24 on Thursday, closed it out.

It’s not like you didn’t know all of those players were around and preparing to try to turn the Nationals from a doormat into a force. But last night, more than any other night so far, you could see them all showing why they provide hope to a franchise that has needed it for years. Their performance made the idea of the Nationals’ becoming the kind of power that fills stadiums and wins pennants feel less like a blurry dot on the horizon. It made that feel like something close to reality.