WASHINGTON -- Luis Angel Firpo do not open their domestic campaign for more than two weeks, and the club received their invitation to compete in the CONCACAF Champions League barely three weeks ago when their Salvadoran colleagues CD Chalatenango were unable to take part in the tournament.But despite that unconventional lead-up to the tourney and the hurried preparations it necessitated, the outfit from Usulután, El Salvador showed precious little rust in their first-leg Champions League qualifying match against D.C. United on Tuesday night.Armed with a savvy game plan and no shortage of skill, Los Toros seized a pivotal early lead and proved quite a handful for their illustrious MLS adversaries over 90 minutes, earning a 1-1 draw at RFK Stadium thanks to an opportunistic goal from Colombian striker Mario Alejandro Benitez -- who was making his club debut for Firpo."They're good, technical players. We knew what was going to happen, I just don't think we executed right. We came out a little bit slow," said D.C. midfielder Andrew Jacobson.Firpo stole the initiative from their hosts with purposeful possession in the early going and Benitez made the most of a mistake by United center back Greg Janicki in the 26th minute, as the Colombian picked Janicki's pocket and lashed a low finish past goalkeeper Milos Kocic."Just a lack of concentration on my part -- brain (cramp), whatever you want to call it," said a mournful Janicki afterwards. "Just a stupid thing. We were just talking about concentrating throughout a game and playing a full 90 minutes, and then I go out and do that."Though the home side equalized on a Jaime Moreno penalty kick before halftime and controlled most of the play thereafter, United's inability to break down the tiring Firpo defense in the second half hands the Black-and-Red a daunting task in the second leg at Usulután's Estadio Sergio Torres in a week's time."We've been through these competitions before, knowing that if you don't take care of your results at home, you're going to be in for a tough environment and difficult circumstances. We didn't take care of our chances today -- we had plenty," said United boss Tom Soehn. "We know what's ahead now. There's no other result than having to go down there and get a win."With his team having played out a 2-2 league draw in San Jose, California 72 hours earlier, Soehn elected to ring the changes in his first XI, rotating in a host of new faces. The move startled Tuesday night's opponents, but also offered motivation as Firpo saw it as a sign that United were taking them lightly."My assistant and I were surprised when we saw the lineup -- we had prepared for a totally different team," said Firpo coach Agustin Castillo.The early goal handed Castillo's squad a dream start but they went on to execute the Peruvian's tactical instructions with aplomb, keeping a high defensive line and applying buzzing pressure throughout the midfield, helping to counteract D.C.'s typical possession dominance. Under the guidance of second-half substitute Christian Gomez, United eventually responded but failed to convert on several promising opportunities before time ran out."They came out with a good plan -- they played with four [midfielders] but they really threw numbers into the center, really clogged the middle for us, which is our strength, our game," said Jacobson. "I think we could've spread the game out a little bit more in the first half. We started doing it second half and got better results."