United midfielder Jaime Moreno injured his ankle in the first half and spent the rest of the night on crutches. It was an omen for the type of night D.C. would have.

After Moreno sprained his left ankle 21 minutes into the game, Marco Etcheverry received a red card in his final game for United for the next month, and D.C.'s defense caved in the second half during a 3-0 loss to the Dallas Burn tonight at the Cotton Bowl. The defeat ended United's seven-game winning streak and was its worst since falling to Kansas City, 6-1, on June 21, 1997.

"We were just awful -- it was very simple," United Coach Thomas Rongen said. "This was just not our game."

Moreno was injured while trying to get open for a shot inside the penalty box. He was confronted by Burn defender Brandon Pollard, who then chopped him down from the side. No foul was called and Moreno did not return, coming back to the field on crutches early in the second half. Team officials said Moreno suffered a second-degree sprain and would be X-rayed Thursday morning. He is expected to miss one to two weeks.

Saturday's game against Los Angeles was supposed to be Moreno's last before leaving to play with the Bolivian national team in Copa America and the Confederations Cup.

Etcheverry, who was playing his last game before also joining the Bolivian national team, got a red card with 16 minutes remaining when he kicked Burn midfielder Leonel Alvarez.

Etcheverry had not been given much room all night by defender Ted Eck and appeared frustrated in the second half. After being dealt the red card, Etcheverry had to be restrained by teammates and Burn players, then kicked water bottles at D.C. United's bench and bumped an assistant referee on the way to the locker room. He spent the final minutes of the game standing, arms folded, in front of the tunnel to the locker room.

United, which beat Columbus, 2-1, Saturday with four players absent for U.S. national team duty, could not overcome the losses of Moreno and Etcheverry tonight.

United (10-4), which surrendered four goals in its last five matches, yielded three in the final 21 minutes, including two to Dante Washington, who had scored just one coming in. Two came after Etcheverry was sent off the field.

"Dallas in the second half just had more legs than we did," Rongen said. "They were able to convert their chances and we weren't."

Washington scored the game's first goal in the 69th minute on a cross from Alvarez, flipping in a header to the upper left corner of the goal.

Teammate Chad Deering scored six minutes later, burning defender Carey Talley, who entered the game as a substitute a minute earlier. Deering nearly made Talley fall on a fake just inside the left side of the penalty box, then punched a shot on the ground to the right post past a diving Tom Presthus.

With United's defenders up near midfield to pressure Dallas, Washington scored again. He took a long feed from Deering and was left with a one-on-one against Presthus. Washington faked a shot to get Presthus on the ground, then calmly knocked in a left-footer to the open net.

The win puts Dallas (8-6) in first place in the Western Conference, two points ahead of idle Colorado.