First base coach Trent Jewett, right, congratulates Kurt Suzuki after the catcher hit a three-run double in Washington’s 14-run, 21-hit onslaught in San Francisco. (Robert Galbraith/Reuters)

Monday night, already looking down on the rest of the major leagues, the Washington Nationals displayed the full extent of their substantial might. They opposed the National League ERA leader and scored two touchdowns worth of runs by the fifth inning, extra points included. Their starter came off a complete game and yielded nothing for six innings. They faced a first-place team and picked their bones clean.

These Nationals can no longer be considered merely an ascendant overachiever. They are a juggernaut, a fact reinforced with jaw-dropping clarity during their 14-2 bludgeoning of the San Francisco Giants at AT&T Park, which matched the largest margin of victory since baseball returned to Washington.

The Nationals have now outscored opponents by 108 runs this season, the best run differential in the majors. As the season has worn on, their dominance has only grown, as if they are only now realizing how good they can be.

“We’re coming together,” said Jayson Werth, who was scratched with right ankle soreness. “It’s the time of year where good teams start to mesh, and the daily grind of spending 10 hours a day together is either wearing on you or it’s making you become a good team. Luckily for us, we’ve got a bunch of good guys and a bunch of guys who come every day, put on their spikes and go out there and play hard. The rest of the stuff takes care of itself. Just keep doing what we’re doing.”

On Monday, they smashed eight runs off Ryan Vogelsong, who had not allowed four all season, and sent him skulking off the mound with two outs in the third inning. Gio Gonzalez shut down the Giants’ previously surging offense, throwing six scoreless innings before yielding a cosmetic two-run homer in the seventh. His 15th win tied him with Livan Hernandez’s total during the 2005 season as the most for any pitcher in the team’s brief history.

An auctioneer would have trouble reading their list of offensive stars. Catcher Kurt Suzuki went 3 for 4 with a game-breaking, three-run double in the seven-run third. Danny Espinosa ripped four hits, including the game’s only homer, a missile to center field in the fifth. Roger Bernadina, playing in place of Werth, swatted three hits and notched three RBI. The Nationals’ 21 hits set a new AT&T Park record and tied their team mark. They sprinted out, and they did not relent.

“I mean, we haven’t had everyone healthy so it’s tough when everyone’s not healthy to put together our offense all the time,” Espinosa said. “Everyone lately has been in a groove.”

By the end of the night, the Nationals had ratcheted Vogelsong’s ERA from 2.27 to 2.72, which left Jordan Zimmermann, Tuesday night’s starter, with the NL lead at 2.35. The victory, combined with the Atlanta Braves’ loss to the San Diego Padres, pushed the Nationals’ edge to 5 ½ games in the National League East, a new high this season and tying their largest lead since baseball returned to Washington. Among division leaders, only the Texas Rangers enjoy a larger cushion.

The Nationals have won 11 of their past 13 games, leveling the best record in the majors at 72-44. Since July 24, the Braves have gone 14-5 — and lost ground in the division. After Monday night’s victory, the team’s public-relations man walked to turn down the clubhouse speakers before Manager Davey Johnson met with reporters.

“It’s going to be hard to turn that music down,” Johnson said. “The boys are in a good mood tonight. Just like the skipper.”

They turned the first phase of their showdown with the Giants, even after scratching Werth with right ankle soreness, into a farce. In four meetings this year, the Nationals have outscored the Giants, a team they may face come October, 38-14.

Before they clobbered the Giants, the Nationals led the National League with 156 runs since the all-star break. They figured to face a difficult challenge in Vogelsong, a right-handed groundball machine. The Nationals had not faced him since 2006, when he was a completely different pitcher and they were a completely different team.

“He throws a lot of strikes, pitches real well down in the zone,” Espinosa said. “If he gives you a pitch in your at-bat, you’ve got to take advantage of it. You just kind of have to take the approach of, you’ve got to get a strike to hit. I’ve never faced him, I don’t know how many guys had. Just get a good pitch to hit.”

The Nationals battered Vogelsong from the first batter of his shortest start of the season, the first time he had not thrown at least six innings. Steve Lombardozzi led off with a single smoked up the middle, and two batters later Ryan Zimmerman doubled him home.

Vogelsong fired a 1-2-3 second inning, which historians may study for its oddity. Gonzalez led off the third with a strikeout, and then the Nationals ambushed. Lombardozzi started the onslaught with a walk. The Nationals would receive good fortune on balls in play, finding empty spaces with groundballs and sinking liners. But luck couldn’t account for the entirety of the demolition.

After Bryce Harper and Zimmerman singled to load the bases, Adam LaRoche walked to the plate. He would be the only Nationals’ starting position player without a hit, but his at-bat helped turn the game. He fell behind, 1-2, before he took three balls, the second right on the edge.

The bases-loaded walk broke the levee. Michael Morse ripped a single off third baseman Marco Scutaro’s glove. Espinosa singled past second baseman Ryan Theriot by inches. Bernadina reached when his liner deflected off Vogelsong. Suzuki provided the crucial blow, a double down the left field line.

Gonzalez struck out again, and then Lombardozzi knocked out Vogelsong with a line drive into right. In the third inning, the Nationals’ position players went 7 for 7 with two walks against Vogelsong.

Once long reliever Brad Penny entered, the Nationals settled for field goals. They scored three runs in the fourth and three more in the fifth. Bernadina’s two-run double off the bricks in right field provided the crucial blow in the fourth, and Espinosa’s mammoth home run keyed the fifth. After five innings, Gonzalez had made four out of the Nationals’ 15 outs, or roughly 27 percent.

“If Gio and I weren’t in there, we’d still be in the third inning,” LaRoche said jokingly afterward.

Fortunately for the Nationals, they acquired him for his left arm. Over 62 / 3 innings, he allowed six hits, walked two and struck out four. He showed no wear from the first nine-inning complete game of his career. In the first, he set the Giants down in order and struck out NL hits leader Melky Cabrera, making him swing and miss twice. In the first six innings, Gonzalez allowed no runs and only one runner into scoring position.

“You got to continue to pound that strike zone,” Gonzalez said. “That’s what everyone kept saying: ‘Keep throwing it, keep throwing it. Don’t try to overthink it. Don’t give them a chance to settle in and come back.’ You just keep attacking and don’t give in. That’s a good hitting team. If you give them any fight back, it could be dangerous.”

The lopsided score and the chill coming off the San Francisco Bay forced many of the 43,050 in attendance to leave early. By the end of the night, seagulls circled the park, expecting the place to be theirs. They were looking for scraps, which were all that remained after the Nationals got through with their latest victim.