Houston’s Ricardo Clark is taken down by United’s Chris Korb in the first half, resulting in a penalty kick being awarded on the play. (Bob Levey/Getty Images)

— It happened again, just like so many other D.C. United visits to this unforgiving destination – a swirl of misfortune in a disorderly moment followed by bewildering reaction.

In a place where nothing has gone right for United, defender James Riley headed a Houston corner kick into his own net in the 80th minute Saturday night, leading to a season-opening 2-0 loss to the Dynamo before 20,019 at BBVA Compass Stadium.

Ricardo Clark secured the outcome in the 89th minute as United fell to 0-10-1 in Houston, many in unusual or excruciating fashion.

Playing without suspended captain Dwayne De Rosario, United survived controversy, a penalty kick and other scares in the first half. It created its own quality opportunities and turned to goalkeeper Bill Hamid to make two mammoth saves.

A tie was within reach, which, all things considered, would’ve been received as a victory. But on Brad Davis’s corner kick, Riley and Clark rose for a header at the six-yard box. Clark failed to make contact and the ball struck Riley squarely and streaked past Hamid.

“Just unlucky. A good ball whipped in,” said Riley, who entered at the start of the second half. “I thought I had him. We both go up. Unfortunately, it goes off my head and in.”

Riley, acquired last month from Chivas USA and entering his ninth season, added: “If it had happened to anyone, I would rather it be me. I am strong enough to handle it and bounce back, no problem.”

The Dynamo is unbeaten in 26 consecutive regular season home games and 31 in all competitions, second in league history behind Real Salt Lake’s 29 and 34, respectively.

With De Rosario unavailable, Coach Ben Olsen employed the same tactics that worked so well for the club in his injury absence last fall: John Thorrington, an offseason signing, joined Perry Kitchen and Marcelo Saragosa in central midfield, leaving Lionard Pajoy as the lone forward.

Predictably, the Dynamo dictated terms and ramped up pressure midway through the opening half. United absorbed and countered. Chris Pontius narrowly missed from distance and then, with multiple options running at the retreating defense, failed to link with Pajoy or get off a shot.

The last six minutes of the half was typically chaotic for a United visit here. Clark ran onto a flicked ball and was apparently clipped from behind by Chris Korb.

The incident began a shade outside the box, but referee Baldomero Toledo awarded a penalty kick.

Hamid read Davis’s walk-up to the shot, slid to his right and blocked the bid without much extension.

Pontius responded two minutes later with a 28-yard free kick that skipped off the crossbar.

“The two, three good chances we had, we’ve got to score those to get out of here” with a good result, Olsen said.

United continued to live dangerously, though. On a 44th-minute corner kick, Korb cleared Will Bruin’s header off the goal line and Hamid made an astonishing save when Giles Barnes tried to bash in the rebound from six yards.

“We survived it,” Korb said.

Olsen turned to his bench at the start of the second half, moving Korb to the left side and replacing Daniel Woolard with Riley.

With Houston’s momentum deflated, the pace turned to United’s liking and there was a growing sense United could not only secure a point but steal three. In the 60th minute, DeLeon caught up to Kitchen’s long ball at the end line and nodded the ball back to Pontius for an open header that streaked high.

Houston regained rhythm midway through the half but failed to convert two chances: Bruin’s six-yard header missed wide and Barnes, after beating the slow-reacting Brandon McDonald to a long ball, scuffed a shot in the box.

Olsen added Marcos Sanchez to the attack, but the ending was all the same: the own goal followed by Clark’s strike, an angled shot over Hamid.

Despite the loss, “To be able to come here where they haven’t lost and be that close to putting those chances away,” Hamid said, “it’s all positive signs.”