FOXBOROUGH, Mass. -- After a promising start, D.C. United's trip to New England ended in frustration.A late penalty kick by Steve Ralston gave the Revolution a 2-1 win against United and left the visitors wondering how it all went wrong."It's a really difficult game to lose after we had what I thought was our best first half of the season so far," United defender Bryan Namoff said. "They came out with a lot of momentum in the second half and we held on. A 1-1 tie with two competitive teams is and should have been the result."Namoff was whistled for the penalty and disagreed with the call, saying that there wasn't much contact between him and Revolution forward Taylor Twellman that led to the 90th-minute spot kick.United coach Tom Soehn didn't like the call either but said his side needed to do a better job of converting its chances."We did what we needed to do, but we need to be more opportunistic and finish our chances," Soehn said. "Then the game's over."Chances came easily to United in the first half as the visitors put together perhaps their best first half of the season. Rodney Wallace went close twice with headers, while Luciano Emilio and Fred also hit the crossbar. New England couldn't get close to United's passing game, but United only had Fred's 36th-minute curler to show for all of their dominance.Buy club jerseys & more today > "We did what Tommy said," Fred said. "We kept the ball and went to it more. We did a great job in the first half, but in the second half, I don't know what happened."All of the fluidity in the first half seeped away in the second half. New England benefited from Taylor Twellman's return -- his first match action since October after struggling with a neck injury -- and Shalrie Joseph's shift back into the center of midfield. Both moves were prompted after Jeff Larentowicz suffered a suspected concussion in the first half.United midfielder Santino Quaranta said the shift changed the game but also attributed some of the shift to not finishing off the match in the first half."They're two good players," Quaranta said. "Of course they are going to change the game. Twellman came on early, but we should have been up 3-0 at halftime, no problem. The game should have been over. That's happened to us a lot this year. It's going to be a let down automatically. You're not going to have a half like that again. It's just not happening on the road. We have to understand that."It didn't happen, and the Revolution took advantage. Shalrie Joseph's 55th-minute header gave New England a foothold in the match and provided the homeside with another boost, Soehn said."Getting the goal gave them life and energy," Soehn said. "We got away from the things we were doing well in the first half."United managed to hold out -- Josh Wicks came out alertly to deny Twellman in a one-on-one opportunity late in the second half -- until the late penalty call sealed their fate. Ralston's goal ended a seven-match unbeaten streak and left United to try to figure it all out."The last five minutes, I don't know what happened," Fred said.