United 3, Fire 2

D.C. United's match with the Chicago Fire on Saturday night had just gotten under way when Freddy Adu attempted a clever turn at midfield to evade two defenders. It's a move the 16-year-old forward has tried many times during his two closely watched seasons in MLS, but on this occasion, he twisted his right leg in an awkward manner.

Adu remained in the game but was treated twice over the next 30 minutes for what was initially believed to be a bruised knee. As halftime approached, however, it became clear the injury was more serious.

After further evaluation on the bench, the diagnosis was changed to a sprained medial collateral ligament, marring United's 3-2 victory and sidelining Adu for at least two weeks.

"I felt it right away when it happened," said Adu, who will undergo an MRI exam Monday to determine the severity of the injury. "They told me to try and run it off to see if it feels better, but I couldn't -- no acceleration whatsoever and I really couldn't cut."

Said Coach Peter Nowak, "He is in such a great run right now, and unfortunately these things happen."

Adu's ailment came at the beginning of a wild evening in front of 14,448 at Soldier Field. Third-year midfielder Brian Carroll scored his first career goal, Dema Kovalenko scored his first of the season in the 72nd minute and Jaime Moreno added a penalty kick six minutes later. But United (9-6-5) had to withstand two late strikes by the Fire (11-8-3) and five hectic minutes of injury time to stretch its unbeaten streak to four games and move within four points of first place in the suddenly crowded Eastern Conference.

"It's such a big win," Kovalenko said. "When we play our game, we're tough to beat. We've just got to get better finishing games. We have to be calmer at the end."

Reserve Lubos Reiter and rookie Chris Rolfe scored within five minutes of each other to provide the unexpectedly tense finish. United, notoriously bad on the road the last five years, is 3-0-1 on its last four trips and a respectable 4-3-4 away from RFK Stadium, where it will play its next three games.

United received a scare 25 seconds into the match when Adu crumpled to the turf in front of the team bench. Attempting to spin past two defenders, the teenager couldn't find any space and was hit on the side of the knee by Samuel Caballero. Adu hopped to the sideline for treatment as play continued and remained out for a little over a minute.

"I had my feet planted so hard that it caused my knee to go inside," he said.

Adu went down again, untouched, in the fifth minute and was consoled by Caballero. John Wilson was set to come in, but the move was rescinded and Adu labored on. He seemed to run without much difficulty, but in the 35th minute, Nowak had to finally pull him.

It was a mostly quiet first half for United's attack, but four minutes before the break, Moreno took charge on the left, cut inside and crossed into the box for Christian Gomez, who deadened the ball and left it for the oncoming Carroll, who one-timed a 12-yard shot past goalkeeper Zach Thornton. It was a good sign for United (7-0-2 when scoring first this year), a bad one for the Fire (0-4-2 when yielding the first goal).

D.C. withstood the Fire's modest pressure in the second half and goalkeeper Nick Rimando overcame a nasty collision with Chicago's Jim Curtin before United extended the lead with a flawless counterattack. Ben Olsen's clearing ball launched Santino Quaranta on a 40-yard run. Quaranta held up at the top of the box before slipping a pass inside to Kovalenko, who took one touch and then angled a low shot past Thornton and into the far right corner.

Later, Gomez was taken down from behind in the box, setting up Moreno's team-high ninth goal of the season. But the desperate Fire applied relentless pressure and caused several anxious moments for United's laboring defenders.

"We shouldn't be in a situation like that," Nowak said, "but overall we had a 3-0 lead, it was comfortable, and I never had a doubt we were going to get three points."

United Notes: Newly acquired defender Facundo Erpen is expected to arrive from Argentina this week, although he won't be eligible to play until the Aug. 20 match vs. Los Angeles. . . . United will play two games next week: Wednesday vs. the MetroStars and Saturday vs. Chivas USA. . . . Former D.C. midfielder Bobby Convey started and played 78 minutes in English club Reading's opener Saturday, a 2-1 home loss to Plymouth. . . . United's reserves (5-3-0) will play Chicago (4-2-2) Sunday morning.

Freddy Adu will have an MRI exam on his right knee, which he injured just seconds into last night's game.