Both goals were scored by substitutes: Memo Rodriguez in the 67th and, about two minutes after he had entered, Tommy McNamara in the 68th.

On the equalizer, United’s Leonardo Jara and Chris McCann failed to interrupt Rodriguez’s run along the top of the penalty area and goalkeeper Bill Hamid, obscured by multiple players, was slow to react to the shot.

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On the go-ahead goal, left back Marquinhos Pedroso mistimed Adam Lundkvist’s cross, allowing McNamara to deflect it past the sprawling Hamid.

United (7-4-3) was reduced to 10 men in the 85th minute when Paul Arriola was red-carded for stepping on an opponent.

Afterward, the coach, the captain and others were angry about the performance, which sputtered through the humid night before an announced crowd of 15,811.

“For stretches of that game, we were asking for it,” Olsen said. “We did give ourselves a good chance -- a good start in the second half -- but again we fell apart in a quick minute or two.”

Rooney said: “We’ve been lucky in games and gotten away with results. Today we didn’t. We didn’t deserve any [points]. As I keep saying, we need to learn. If we can’t when we are at the top [of the conference], we never will.”

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Arriola added, “We’re all frustrated from the way we played from the first minute.”

And defender Steve Birnbaum said: “They were the better team for the most part. We didn’t have the composure to keep it and make them work. It was sloppy from us and they capitalized on some of our mistakes. Give them credit, but it wasn’t good from us.”

United has posted four shots on target over the past two matches and conceded possession at alarming rates.

D.C. remained even on points (24) with Philadelphia (7-3-3) atop MLS’s Eastern Conference but settled for second place on goal differential and matches played.

After starting five typical subs Wednesday in Toronto — and surviving a 35-3 shot deficit to gain a 0-0 draw — Olsen turned to a stronger lineup here. There were, however, two notable absences and a positional change.

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Junior Moreno missed his second consecutive match to be with family following the death of his father, and Chris Durkin is in Poland with the U.S. under-20 national team for the U-20 World Cup.

With two defensive midfielders away, Olsen turned to the versatile Arriola to partner with Russell Canouse behind playmaker Luciano Acosta. In Arriola’s preferred position (right flank), Ulises Segura made his fifth start.

The match got off to a frightening start when, in the first minute, Birnbaum crashed heads with Alberth Elis. Both required treatment before returning. With blood flowing from the top of his head, Birnbaum needed a head wrap and fresh jersey.

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In the 10th minute, however, Elis (four goals, team-high six assists) could no longer continue.

“I came in a little late,” Birnbaum said. “I just hope he is all right.”

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Houston (7-2-2) began to put its mark on the match after 25 minutes. With the Dynamo in charge and the Acosta-Rooney partnership in seclusion, United rarely sustained quality possession.

Those problems dissipated less than a minute after intermission. Canouse disrupted a Houston attack. Lucas Rodriguez raced into space before connecting with Acosta, who pushed the ball wide to Segura for a low effort past goalkeeper Joe Willis.

In his illustrious career, Rooney has not scored many goals as easy as this one. Left unmarked on the back side, he tapped in from three yards — his seventh goal of the year and 19th in 33 matches since je joined United last summer.

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Olsen then inserted McCann for Segura, and although many were at fault, things began to unravel. Rodriguez danced past passive resistance and beat Hamid to the low right corner. McNamara then beat Pedroso to the ball and shattered the deadlock.

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On the substitution, Olsen said: “We wanted to get more passing in the center of the park. That’s a position Chris plays, and we wanted to get Paul back to his natural position. It was in the plans going into the game, and we still thought it was the move that would settle the game down. I’ll take that [blame] if we need to put that on somebody.”

Facing a deficit, United was out of gas and out of ideas. Arriola’s expulsion all but extinguished its hopes. He will sit out Saturday at New England (3-8-3).

“It was accidental, but the referee said it doesn’t matter,” he said. “I put myself in a position. I put the referee in a position to make a decision. That’s on me.”

The performance and the result left everyone in a foul mood.