PHILADELPHIA - With the Washington Nationals facing an uphill climb to get back in the divisional race in mid-September, Jayson Werth is sharing his past experiences with teammates. He is also sharing a bat that has heated up in the season's final month.

Behind another pair of Werth home runs as well as Bryce Harper's 40th homer of the season, the Washington Nationals thumped the Philadelphia Phillies 12-2 Wednesday night to complete a series sweep.

It was the fourth straight win for the Nationals, who gained a game on the National League East-leading Mets. Washington still sits 7 1/2 games back with 17 games left on its schedule, and while winning the division is not likely, it's not impossible. Werth knows firsthand and was part of a Phillies team that overcame a seven-game deficit with 17 games to play to take the NL East from the Mets in 2007.

"Everybody knows, everybody is aware," Werth, the left fielder, said after the game. "You got to believe and a lot has to happen."

The Nationals offense did its part Wednesday night. Werth had a multi-homer game for the second time in the series against his former club, and he now has six homers and 13 RBIs in 15 games this month.

Washington totaled 16 hits, and five players had two RBIs in the rout. One of those players was Harper, a right fielder who left the yard in the seventh inning to hit the 40-homer plateau as a 22-year-old. The 40 homers are the most in the NL as Harper pulled ahead of Colorado's Nolan Arenado.

"It's just unbelievable," Nationals starter Gio Gonzalez said of Harper. "I don't think in my career I've ever played with a guy who has hit 40 homers. And he's 22 years old, he has the world in his hands. The sky is the limit and that is an understatement. I think he has more than that."

Gonzalez was sharp himself Wednesday, tying a career-high with 12 strikeouts in seven innings. The veteran lefty surrendered five hits, walked a pair of hitters and registered 10 or more strikeouts for the second time this season.

"Everybody in the lineup helped out a lot," said Gonzalez, who previously struck out 12 against the Mets on Sept. 25, 2014. "And a lot of credit goes to my catcher (Joe Lobaton), he called a great game. He mixed it up a lot, increased my confidence and slowed it down for me."

The Phillies got their only offense of the game in the fourth inning when first baseman Darin Ruf launched a towering two-run homer to left field. Second baseman Andres Blanco, who singled to start the inning, scored on the homer. But the Phillies had just three other hits in the game.

Philadelphia struck out a total of 13 times in the game and had at least that many strikeouts in all three games in the series against Washington. Forty-two of the Phillies' 87 outs in the series (48.3 percent) came via strikeouts.

The Phillies lineup is filled primarily with rookies and other players who are not used to playing every day in a major league lineup. Manager Pete Mackanin chalked up some of his team's poor at-bats to players not having experience this late in a campaign.

"A lot of these guys haven't played this deep into a season," he said. "I think it's getting to them a little bit and they have to learn to get over that hump."

The team also had a young player on the mound as starter Alec Asher was making his fourth career start. He was charged with four earned runs on seven hits in five innings, and the 23-year-old has given up at least four earned runs in every major league start he's made.

"Is it too soon to have him make this jump? I don't think so," Mackanin said about Asher pitching in the majors. "It's best any time you can get a guy in the major leagues to see what he is working with."

The Nationals continued their offensive assault on the Phillies bullpen.

Philadelphia's combination of relievers (Hector Neris, Justin De Fratus, Nolan Ogando and Ken Roberts) surrendered eight runs (seven earned) in four innings.

Washington returns home hoping it can continue to swing the bats well and gain more ground on New York.

"We have to come in here with mentality to win ballgames," Harper said. "And if our lineup does what it needs to do, it's going to be pretty special to figure it out and win ballgames."

NOTES: The Phillies shifted their rotation before Wednesday's game to have RHP Alec Asher start in the series finale against Washington. Rookie LHP Adam Morgan, who was originally supposed to pitch against the Nationals, will start against the Braves on Friday after the Phillies' off-day on Thursday. Morgan has thrown 78 1/3 innings in 14 starts since debuting on June 21. ... OF Aaron Altherr returned to the Phillies' lineup after being held out of Tuesday night's 4-0 loss with a bruised elbow. Altherr entered Wednesday's game with a .839 OPS in 24 games this season. ... Washington RF Bryce Harper's 40 home runs are the most ever by a left-handed Nationals batter. Harper topped Adam Dunn on that list but still trails right-handed-hitting Alfonso Soriano, who hit 46 homers in 2006, for the franchise season record.