Dan Haren, who scored a run on a Bryce Harper homer in the third inning, allowed only one run on three hits in seven innings of work on the mound. (Toni L. Sandys/The Washington Post)

Very little about this Washington Nationals season has unfolded as expected. Four days from August, they sit three games under .500 and 81 / 2 games back of first place in a weak National League East. Their talented lineup has dragged down the rest of the team. Mediocre opposing pitchers have baffled Nationals hitters. One of their biggest offseason acquisitions, a leadoff hitter, is no longer their everyday leadoff hitter. Their highest-paid pitcher is enduring one of the worst seasons of his career.

On Saturday, after a busy and eventful week, the Nationals flipped several season-long trends on their heads in a 4-1 win over the New York Mets. The offense erupted for three home runs, including a two-run shot by Bryce Harper. The lineup finally solved middling Dillon Gee after poor hitting displays against him all season. Denard Span snapped a long four-month power drought with his first home run of the season. Dan Haren tossed seven strong innings, another encouraging development in his second-half improvement.

The Nationals began the second half of their season in horrid fashion: a six-game losing streak, the demotion of their former closer Drew Storen and the firing of hitting coach Rick Eckstein. Entering Saturday, a 2-7 stretch since the All-Star Game had created a larger feeling of uneasiness about this team. But much like spot starter Ross Ohlendorf did the night before, Haren stemmed the tide. Haren said the Nationals’ morale hit a season low following an 11-0 drubbing by the Mets in the first game of Friday’s doubleheader.

“We don’t have any time for hitting rock bottom anymore,” he said. “That’s it. If we’re going to hit rock bottom, that was it, and we have to go from there.”

Haren, whose performance could be one of the determining factors of the Nationals’ second half, allowed only one run on three hits, two of them in the sixth inning. He commanded his fastball better than in past starts, keeping his pitches mostly low in the strike zone. He maintained a larger gap in between his fastballs, which averaged 89 mph, and his 85-mph cutters and 83-mph split-fingers. He needed 103 pitches to carve through seven innings, walking into the dugout after the 21st out to the applause of a frustrated fan base. The two hardest hits balls he allowed — towering shots by David Wright — went foul. Saturday was Haren’s first win since May 9.

The Post Sports Live crew debates whether the Nationals can still make it to the postseason, despite the hole they have dug themselves. (Post Sports Live)

“We’re a few games under .500, and a big reason for that is me, among other guys, but I take a lot of the blame,” he said. “It feels good having a good game, and I want to keep it going.”

In his first 15 starts of the season, Haren was among the worst pitchers in baseball with a 6.15 ERA. In his four starts since he returned from the disabled list with shoulder inflammation — more than anything a chance for him to rest and regroup — Haren has a 3.13 ERA, which includes a game in which he allowed five runs. The back end of the Nationals’ rotation has struggled or been hurt, a cause of concern ahead of Wednesday’s trade deadline. But Haren’s recent improvements have given Manager Davey Johnson more proof in his already strong belief the right-hander can keep this up.

“He’s a veteran,” Johnson said. “He’s got it now.”

Like Haren, Span has struggled to find a groove this season. The outfielder’s timing and swing have been off. In a new league, he has not been able to fully adjust. His lack of production dropped him to seventh in the lineup. And while he didn’t notch a hit in his two other at-bats, Span’s homer was a welcome surprise.

“It was good to see him do that,” Harper said, before joking. “Hopefully he doesn’t get too cocky and stay a little humble.”

The power surge against Gee began in the second inning. Little about the Nationals’ offense this season has made any sense. Entering Saturday’s game, Gee had allowed only three runs in 182 / 3 innings spread over three starts against the Nationals for an ERA of 0.96. Against everyone else, Gee has posted a 4.56 ERA.

But in the second inning, Ian Desmond belied his normally aggressive nature and worked a seven-pitch at-bat. Gee threw a change-up, and Desmond clobbered the ball on a line drive to center field for a solo home run. On the next pitch, Span followed with a home run of his own.

Span smacked a fastball into the right field seats, a sign of his newfound aggression hitting lower in the lineup. By no means is he a power hitter; he had 23 career home runs entering Saturday. But 105 games into the season, he finally got to break out a rusty home run trot and snap a streak of 426 plate appearances without a long ball.

“I think I stutter-stepped around third,” he said. “I was just trying not to fall.” Later, he joked: “I tell you what, after hitting one today, it felt like I might hit 30 for the rest of the season, so you guys watch out for me.”

The Nationals tacked on two more runs an inning later. Haren led off the third with a laser double to center field off Gee. Harper, the Nationals’ leadoff hitter in place of Span, then drove a fastball just over the center field fence for a 4-0 lead.

The back end of the Nationals’ bullpen — a recent lightning rod given Storen’s demotion, closer Rafael Soriano’s presence and Tyler Clippard’s criticism of the organization over Storen — sealed Haren’s gem. Clippard continued his mastery with a scoreless eighth inning, his 15th straight spotless appearance, which lowered his ERA to 1.74.

After a 62-minute rain delay interrupted the bottom of the eighth, Soriano pitched a scoreless ninth for his 26th save of the season. Following days of lowly play, roster changes and struggles, the Nationals finally found order for one day.

“We’ve been up and down all season,” Span said. “Every time it seems like we have a dramatic victory, we think we’re getting ready to turn the corner and then all of a sudden we’ll lose a series or lose a few games in a row. Right now we’re just trying to take one game at a time and just enjoy each victory as they come.”