Zoltan Stieber breaks in to give D.C. United an insurance goal late in the second half. (John McDonnell/The Washington Post)

D.C. United earned 18 points over the first five months of the MLS season, and even with most of the remaining matches at its new home at Buzzard Point, the playoff outlook remained grim. There was too much ground to make up and there were too many games packed into a congested schedule to reach the postseason threshold.

But over three games in eight days at Audi Field, United has rejuvenated the campaign, and with a nine-point rush, D.C. has joined the scramble for the last few slots.

Luciano Acosta continued his searing form, and United played with confidence and joy, defeating the New England Revolution, 2-0, on Sunday before an announced sellout crowd of 20,198 to extend its winning streak to three and unbeaten run to five.

In a little more than a week, United (7-9-6) equaled the number of victories it had achieved through the first 15 matches (three).

“It shows how quickly,” midfielder Paul Arriola said, “things can change in the league.”

The club remains in eighth place but is now two points behind seventh-place New England (7-9-8); six in back of Montreal (10-13-3), which has played four additional matches; and six back of Philadelphia (10-11-3), which has played two extra games. The top six will qualify for the playoffs.

“We put together three good performances,” goalkeeper Bill Hamid said. “I don’t want us to lose our heads right now, but we’re trending in the right direction. The way we are playing football, the way we dominated this team, the way we put it together against Portland [a 4-1 result Wednesday], the chemistry is very solid right now.”

United had not won three in a row since last August (all by 1-0 scores). The team not only is getting better but has become fun to watch. From the start Sunday, D.C. was in control. Acosta scored early, and Zoltan Stieber struck late as United beat the Revolution in Washington for the seventh consecutive time and earned its first shutout since April 14.

“This was a great week,” Coach Ben Olsen said. “It was a long week. I asked a lot from these guys, mentally and physically. They dug in, and at times there were some great stuff, some great soccer throughout the week.”

Acosta’s partnership with Wayne Rooney continues to grow and prosper, and it has become a collaboration that has turned United into a profoundly dangerous team.

D.C. pinged the ball around fluidly and made use of both flanks, stretching the Revolution (winless in seven straight) to the point of breaking. United was particularly enamored with the right side, where outside back Oniel Fisher overlapped so often it was hard to tell whether he was a defender or attacker.

United also dealt with the Revolution’s physical style. “They came here to pick a fight,” Olsen said. Added Hamid: “They like to bully teams. They like to fight. They throw punches. They have late tackles. They just scrap all over the field. We were prepared for it.”

Scott Caldwell was red-carded in the 73rd minute after a second yellow card.

United went ahead in the 13th minute. Arriola received a cross-field pass from Acosta and worked on Brandon Bye before crossing through the six-yard box. In stride on the back side, Acosta smashed an angled one-timer from eight yards that took flight and streaked into the roof of the net for his fourth goal (plus one assist) in three matches.

Andrew Farrell bailed out the Revolution five minutes later, clearing the ball behind Matt Turner after Acosta’s effort from beyond the box eluded the goalkeeper.

The Revolution showed notable improvement after intermission, keeping the ball and keeping Hamid on his toes. The first serious bid came 10 minutes into the half when Diego Fagundez’s rasping drive smacked the outside of the near post.

United’s outlook brightened when Caldwell’s ejection left his team with 10 men. Blessed with the same situation against Orlando last weekend, D.C. conceded the equalizer before answering in stoppage time.

There were no such issues Sunday. The defense stayed disciplined, and after Rooney squandered a breakaway in the 86th minute, Stieber took advantage of New England’s commitment to the attack by collecting Junior Moreno’s pass over the top of a thinning defensive corps and beating Turner on a breakaway for his fifth goal.

And with a fifth victory in six appearances at Audi Field, United finds itself in the playoff hunt.

“It’s doable, but it’s going to take more than nine points in one week,” Olsen said. “We’ve got to keep climbing.”

Notes: D.C. will visit the second-place New York Red Bulls next Sunday night. …

Moreno, who started for the fourth time in five games, was named to the Venezuelan national team for friendlies against Colombia on Sept. 7 in Miami and at Panama on Sept. 11. He will miss the Sept. 8 visit to New York City FC and the Sept. 12 home match against Minnesota United.