The Union's first-ever Major League Soccer playoff game consisted of dominance in possession, pressure, and scoring chances.

None of that mattered as the Union suffered a 2-1 loss to the Houston Dynamo in the first leg of this Eastern Conference semifinal - a two-game, aggregate-goal series - on Sunday before a sellout crowd of 18,539 at PPL Park in Chester.

Thus the Union will, in essence, start Thursday's MLS Cup game in Houston a goal down. If the teams are tied in total goals after Thursday's regulation, two 15-minute overtime periods will be played in their entirety. If the score remains tied at the conclusion of the additional 30 minutes, the series winner will be decided by penalty kicks.

For the Union, the key is now getting that equalizer, something that eluded them in the opener.

"We made too many mistakes in the first half, and that is difficult to overcome," Union team manager Peter Nowak said.

The Union trailed, 2-1, after the first 45 minute in an up-tempo first half. In the second half, the Union did everything but score.

The Union, who were 7-1-9 at home during the regular season, came out with a new formation, utilizing five defenders. Stefani Miglioranzi, who had played just one minute in the last five games, started as a third central defender along with Danny Califf and Carlos Valdes.

That allowed outside defenders Gabe Farfan and Sheanon Williams to push more on the attack.

And in the beginning of the game, there was plenty of offense from both sides.

Houston opened the scoring in the fifth minute when Brad Davis sent a well-placed pass from about 40 yards out into the box, where Andre Hainault headed it in from the six-yard line.

Davis was the MLS assist leader with 16 this season, and he is known for his impeccable accuracy on long kicks. It was certainly demonstrated on that play. It's no wonder Davis is being mentioned as an MVP candidate.

"They were trying to get a lot of numbers in the midfield, and it was tough to control, and they did a good job of moving the ball. But on the other hand, I think we defended pretty well," Davis said.

The Union got the equalizer when Sebastien Le Toux one-timed a Michael Farfan cross in the seventh minute. Farfan had taken a pass from Justin Mapp and sent the ball to the near post. Le Toux tapped it in for the Union's first MLS Cup playoff goal.

"The pass was actually deflected to me, and I was lucky to get it on my run and put my left foot on it," said Le Toux, who led the Union with 11 goals in the regular season.

The Dynamo took a 2-1 lead in the 30th minute on a great give-and-go from veteran Brian Ching to Calen Carr. Ching sent Carr on goal, who hit it in from the six-yard line just before he was upended by Valdes.

While the Union were attacking with their outside backs, Houston was able to counter by working the middle of the field and was effective with a much shorter passing game than the Union.

The Union put continued pressure on Houston in the second half.

In the 55th minute, Danny Mwanga shot wide from a scramble inside the box, but the Union's best second-half chance came when Jack McInerney's header of a Freddy Adu cross went off the cross bar in the 88th minute.

"I thought it was going to chip under the bar," McInerney said. "I thought I was pretty lucky to get my head on it and barely got a piece of it."

His team wasn't as fortunate, and now they have 90 minutes to attempt to make up a one-goal deficit.

Phillies, Flyers represent. Before the game, Phillies shortstop Jimmy Rollins and Scott Hartnell and James van Riemsdyk of the Flyers were named as honorary captains.

This article contains information from the Associated Press.