The Philadelphia Union slumped to their second defeat in the last three matches, falling 1-0 to FC Dallas at Toyota Stadium.
Jesus Ferreira scored the only goal of the match in the 34th minute, his team-leading ninth of the season.
Philadelphia remains atop the Eastern Conference despite the loss while Dallas moves to third in the Western Conference as the Hoops remain undefeated against the Union at home.
Story of the match
There weren't many chances in the opening stages of the match as Philadelphia pinned Dallas in their own end and trying their luck with set pieces.
On 17 minutes, the hosts played a long ball over the top for Paul Arriola, who fired wide from a tight angle. At the other end, Martin Paes saved from Julian Carranza.
Dallas was hoping for a VAR review as a shot by Ferreira deflected off of Jack Elliott and into the arms of Andre Blake, but replays showed that the ball didn't come off of the defender's arm.
The Hoops went in front as Arriola strode down the right and found Ferreira on the right edge of the box and got around Jakob Glesnes to beat Blake at the far post.
Alan Velasco then tested Blake from distance with the Union 'keeper up to the challenge and play was stopped for treatment on Cory Burke following a collision and Mikael Uhre came on for him in first-half stoppage time.
At the start of the second half, Blake was forced into a save at his near post from a Ferreira effort and five minutes later, he looped a ball for Arriola, who somehow shot wide.
The visitors then had an opportunity as a cut-back by Leon Flach sent the ball to Uhre, the Dane seeing his shot stopped by Paes.
In the 59th minute, Philadelphia manager Jim Curtin introduced Jack McGlynn and Oliver Mbaizo for Flach and Nathan Harriel.
Daniel Gazdag then won a free-kick after being fouled on the edge of the area, but McGlynn's strike was on the ground and didn't bother Paes.
With three minutes remaining, Paxten Aaronson and Chris Donovan replaced Jose Martinez and Carranza, but it did Philadelphia no good as Dallas saw out the victory.
Man of the match: Jesus Ferreira
He continues to make his case for inclusion into the US national team with another well-taken goal with his turn, control and finish of the highest quality.