“When the losses start to pile up, it becomes emotional,” said D.C. United Coach Olsen, pictured above earlier this month. “We have to, first and foremost, stay together right now. It’s an easy time to point fingers. I don’t think our group is at that stage. They are able to dig out of this.” (Jonathan Newton / The Washington Post)

CHESTER, Pa. — D.C. United’s plunging season reached fresh depths Saturday with a disastrous first-half performance that called into question not only the team’s postseason outlook but its heart.

Ben Olsen’s wayward gang fell behind within minutes of kickoff and by three goals well before halftime in a 3-1 defeat to the Philadelphia Union.

The defense was in shambles, and the attack was toothless without Wayne Rooney, though even if the suspended captain had played, it’s hard to see United reclaiming the pulse of a onetime Eastern Conference contender.

“When the losses start to pile up, it becomes emotional,” Olsen said. “We have to, first and foremost, stay together right now. It’s an easy time to point fingers. I don’t think our group is at that stage. They are able to dig out of this.”

A seemingly secure MLS playoff berth is in danger as the point cushion narrowed after a third consecutive defeat and the continuation of a summer swoon: 2-6-3 since late June and 3-7-7 since mid-May.

United (10-10-9) retained fifth place by a point over New England in a conference that will send seven to postseason, but with just five matches left and other teams having more games on the schedule, D.C. is running out of time to end the late drama and turn the corner.

“Very concerned. Been concerned for a while now,” defender Steve Birnbaum said. “We haven’t found that turning point. ... The season is slowly slipping away right now. I don’t know what it is, but we’ve got to figure it out.”

Second-place Philadelphia (14-8-6) has won six straight regular season matchups between the regional adversaries by a combined 18-4.

Rooney (team-best 11 goals) has missed three of the past seven matches for family reasons and minor injuries (Atlanta), illness (Los Angeles Galaxy) and red-card suspension (Philadelphia). In all likelihood, because he was expelled for a blow to the head against the New York Red Bulls on Wednesday, the MLS disciplinary committee will extend his ban to Saturday’s match at Montreal.

Rooney’s latest absence placed greater burden on newcomer Ola Kamara to produce. He scored a sensational goal from distance Wednesday, and with his fitness level gradually improving, United turned to the Norwegian national team forward to fill Rooney’s shoes.

Rooney’s absence also opened a slot for Luciano Acosta, the Argentine playmaker who was relegated to bench duty two weeks ago. The demotion comes at a time when United is listening to transfer offers from clubs overseas, such as Saudi Arabia, before international windows close in the coming weeks.

Three weeks after a 5-1 home defeat to Philadelphia, United was in trouble after less than five minutes before a sellout crowd of 18,781 at Talen Energy Stadium.

As Philadelphia’s Kai Wagner and Brenden Aaronson worked the left side, Kacper Przybylko made a diagonal run inside the penalty area. He left behind one center back (Birnbaum) and stepped in front of another (Frederic Brillant) at the near post to one-time Wagner’s cross past Bill Hamid for his team-high 12th goal.

D.C. has conceded at least one goal inside 20 minutes in three of the past four matches. “They are killing us,” Olsen said.

“We understand that is a big problem,” midfielder Paul Arriola said, “and we do it again.”

Eleven minutes later, the Union exploited the heart of D.C.'s resistance. Przybylko sidestepped Brillant, whose advanced position left the back exposed. Aaronson, 18, gathered Przybylko’s pass behind defensive midfielder Junior Moreno and coolly slotted a low shot into the left corner.

The deficit grew in the 36th minute. Przybylko connected with Ilsinho, who accelerated past the flat-footed Moreno and beat Hamid to the far corner.

Acosta cut the deficit in the 56th minute, using his quick footwork to penetrate, recover possession and slip the ball past Andre Blake for his sixth goal. The addition of Quincy Amarikwa, Emmanuel Boateng and Lucas Rodriguez provided fresh attacking weapons, but Philadelphia absorbed moderate pressure.

“We didn’t really understand how to deal with their overloads” on the flanks, Arriola said. “We lacked ideas going forward. We lacked legs and a finishing touch. Defensively we weren’t good collectively.”

Note: Defender Jalen Robinson, who started two of the previous three matches, did not travel because of a knee injury. An MRI exam was inconclusive and United is unsure whether he will return soon or require surgery.

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