D.C. United has burst from last place into playoff contention just 16 matches after acquiring Wayne Rooney and opening its new stadium. (Geoff Burke/USA Today Sports)

Early in the summer, when D.C. United was sitting at the bottom of MLS’s Eastern Conference standings for weeks on end and the only glimmer of hope rested with a new stadium rising at Buzzard Point, a playoff berth was a preposterous suggestion.

But then “Señor Wayne” arrived, and the little guy from Argentina who coined that nickname forged. The defensive midfielders healed, the goalkeeper returned from Europe and chemistry took hold.

The 20,000-strong venue opened, and not only were the supporters tickled by the fresh paint and sweet sightlines, they had something exciting to watch.

Some three months later, amid a soccer renaissance at Audi Field, United is in an improbable playoff race entering the final three weekends of the regular season. A victory over Western-leading FC Dallas on Saturday would elevate D.C. to its highest position since the first week of the campaign and, of greater consequence, lift it above the postseason threshold.

With six playoff slots available, United (11-11-8, 41 points) is two points behind sixth-place Montreal, which is idle this weekend. D.C. has played two fewer matches and, by winning three of the last four, would clinch a berth regardless of how the Impact fares in its last two games.

It’s been a stupendous rise. Since starting 2-7-5 (with 12 road games and two at temporary homes in the metro area), United has gone 9-4-3. Its record at Audi Field is 9-2-1 with 29 goals for and 14 against.

“It’s hard to step back and enjoy this run because we have so much work to do,” Coach Ben Olsen said of the final act. “Every time we get a big result, we exhale and then we’ve got to go do it again in a must-win game. That’s the bed we’ve made.”

United is sleeping better than ever. The current unbeaten streak (4-0-2) is the longest in the 23-team league at the moment. (At five games, Dallas is second.) D.C. will play three matches at home — eliminated Toronto FC and playoff-bound New York City FC will follow Dallas — before closing at 10th-place Chicago.

The roster is mostly healthy. The regulars are rested. Confidence is high.

Even after the slow start this year, midfielder-defender Paul Arriola said, “there was still a lot of optimism about where we could go this season. We never thought we weren’t good enough."

With the schedule and odds stacked against his team at the start, Olsen understood United “would have to make one hell of a run to get into the playoffs. And that’s where we are. We’re in the conversation and we have an opportunity to be in the postseason.”

United is in the conversation, in large part, because of Wayne Rooney, the English superstar who arrived midseason with the largest contract in organization history (an estimated $5 million per season). Obliterating concerns about his age (32) and desire, Rooney has scored two goals in each of the past two matches, five in three games and nine in 16 appearances overall, along with seven assists.

“He’s been unbelievable,” defender Steve Birnbaum said.

Beyond the production, United believed it was acquiring a leader and influential figure. Three weeks into his MLS tenure, Rooney was named team captain.

“When we knew we were getting Wayne,” Olsen said, “we talked about him elevating players around him.”

No one has grown, figuratively, more than Luciano Acosta, the 5-foot-3 playmaker from Argentina whose spotty production and short fuse have, at times, overshadowed his skills since joining signing at the start of the 2016 season.

Before Rooney’s arrival, Acosta recorded one goal and seven assists this year. Since, he has posted eight goals and nine assists.

Because the pair plays close together in the attack, Olsen said he had hoped Rooney would help Acosta “take his game to the next level."

Perhaps reflecting on past issues with Acosta, Olsen laughed and said, “I certainly couldn’t get him there.”

On the humming partnership, he said, “I didn’t expect it to be that immediate and this productive.”

Rooney said he has been a little surprised, given the team’s predicament and the midseason changes, by how well United has performed as a whole.

Asked about his expectations upon arriving, he said: “Realistically, it was to try to build momentum for next season. Making the playoffs, being so far away, wasn’t a realistic target. But with every game and as each week went along, we put ourselves in a position it was realistic. That is where we are today.”

Building chemistry, especially with new players arriving midseason, is never easy.

“It could’ve been easy for guys to come in and say this season is done,” Arriola said. “We’ll see what we can do and, if we get somewhere cool, great. If not, we’ll try again next year when we get a full year together. But we have guys who brought the right mentality, brought energy and wanted to be part of the group.”

United’s rise has been fueled by additional factors:

Goalkeeper Bill Hamid rejoined the team in August after a short and unsuccessful tenure in Denmark. United was not necessarily looking to replace starter David Ousted, Olsen said, but Hamid’s interest in returning to MLS was “an opportunity we needed to explore.”

Hamid has performed better than Ousted, and he has also received better protection. With Hamid, a tighter back line and a stronger midfield, United has conceded multiple goals just four times since mid-July.

Defensive midfielders Russell Canouse and Junior Moreno are healthy and in sync. Before they began starting together in late July, Olsen relied on a single player in that role: teenager Chris Durkin.

Durkin gained valuable experience and performed well overall, but, Olsen said: “We were getting exploited. We were scoring goals but giving them up at the same rate. It wasn’t sustainable.”

The dual formation has provided support for Acosta and shielded the center backs. Durkin, 18, has filled a reserve role of late, but with Moreno on international duty with Venezuela, he is likely to start the next two games.

At a time of year when physical and mental fatigue sets in, United has embraced the home-friendly calendar (15 of the final 20 matches are at Audi Field). The only trips the past three months were easy ones: Atlanta, Montreal and New York (by train) twice. In contrast, in one particular seven-week span, United visited Salt Lake City, San Jose, Los Angeles twice and Seattle.

As for reaching the playoffs, United is in contention for a prize that seemed out of reach not so long ago. It was last in the conference from early May until mid-August before taking flight.

The margin of error remains small, “but the guys are up for it,” Olsen said. “They have a good balance of winning and enjoying the moment with the understanding we have another very important stretch now. The urgency has to be on this game — and then the next one and the one after that.”

***

D.C. United vs. FC Dallas

Where: Audi Field.

When: Saturday, 4:55 p.m.

TV: Univision.

Records: United 11-11-8, 41 points; Dallas 16-6-9, 57 points.

D.C. probable starters: GK Bill Hamid; Ds Paul Arriola, Frederic Brillant, Steve Birnbaum, Joseph Mora; MFs Zoltan Stieber, Chris Durkin, Russell Canouse, Luciano Acosta, Yamil Asad; F Wayne Rooney.

Dallas probable starters: GK Jesse Gonzalez; Ds Ryan Hollingshead, Matt Hedges, Reto Ziegler, Marquinhos Pedroso; MFs Michael Barrios, Roland Lamah, Victor Ulloa, Maxi Urruti, Santiago Mosquera; F Dominique Badji.

***

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