WASHINGTON -- In the aftermath of D.C. United's 2-1 win over FC Dallas at RFK Stadium on May 2, Santino Quaranta entertained several reporters in front of his locker, genially talking soccer long after most of his teammates had showered and left the building. Despite the evening's positive result, he was lamenting his team's inability to convert their possession and attacking menace into goals, a lack of killer instinct which greatly complicated their task that night."How long does that keep happening, you keep getting so many chances and not finishing the game off?" wondered the United veteran. "I think that we showed that we were the better team tonight. But it is frustrating sometimes, man, to play like that. Same thing happened in New York [the previous week]. You can't leave a team like that around."Subsequent results have only reinforced the reasons for Quaranta's concern. United failed to maintain their first-half lead in Kansas City and Toronto FC's cagey tactics nearly allowed the Reds to steal three points from their visit to RFK Stadium, only to be denied by another last-call flurry from the Black-and-Red. Both matches ended in ties but D.C. fans could be forgiven for viewing both occasions as two points lost."We're not putting teams away," said head coach Tom Soehn this week. "That's coming back to bite us a little bit. The fact that we are having to squeak out results at the end of the game, that we have to get better at. But we also have to get better at eliminating our mistakes that are causing the goals."If Soehn and his men seem to be focusing on the bright side, it's for similarly understandable reasons: a more well-rounded squad has exhibited far more cohesiveness and quality than last year's group had by this point. A year ago, D.C. were 2-5 in league play and still smarting from a semifinal exit in the CONCACAF Champions Cup."We are playing a pretty attractive brand of soccer, the type we try to play, we are creating a lot of opportunities and we are limiting opportunities on the other side," added Soehn. "So we are going in the right direction, but we still have some things to shore up, as I would expect this time of year."Some areas bear all too much familiarity to past versions, starting with a defense boasting tremendous potential yet still prone to untimely breakdowns and mental mistakes.From 2005 to 2007, the club routinely produced the league's best soccer but backline fragility in do-or-die circumstances prevented further additions to the RFK trophy case. New arrivals this year, goalkeeper Milos Kocic and center back Dejan Jakovic might eventually become the bedrock upon which competitive United squads are built for years to come.But the Serbian-born youngsters gifted Toronto their first goal on a basic miscommunication that could prove grievously costly in more pressure-packed circumstances."We were letting the balls bounce from the goalkeeper's punts, you know?" said Quaranta. "You can't let that kind of stuff happen at this level, or you're going to get hurt. And it's a learning process for us, but that's just fundamental stuff that we have to figure out."Conversely, tired legs surely played into Bryan Namoff and Clyde Simms' sluggish reactions to Dwayne De Rosario's solo run on TFC's third tally."We just fouled up a couple plays that hopefully we will learn. The important thing is that we learn from the stuff we do wrong. Can we fix those things? They're not lessons unless you learn from them," said Ben Olsen. "Going forward, we can not be in these situations where we dominate and then lose concentration for a minute here, a minute there and then all of a sudden we are tying at home."Of the 13 goals D.C. have allowed this season, 11 have been surrendered in the second half, the sort of ratio that usually reflects late heartbreak. Soehn often preaches the virtues of 'match management,' and Olsen has been pivotal this season in large part because his vast experience has given him a situational awareness that tends to be an elusive trait among younger professionals."The concentration over a 90-minute span is always tough, especially for guys that are coming into the game and not used to being punished for that one minute -- or that one second, rather -- that you take off," said the former U.S. international.To consolidate their present position atop the standings, United will need to be imperious at RFK, where visiting sides are likely to continue the bunker/counterattack model used by New England and Toronto -- and resolute on the road.This weekend's trip to southern California for a meeting with league pacesetters Chivas USA presents an opportunity for United to display progress on the latter front. The margin for error is typically razor-thin against Preki's side, who are excellent at The Home Depot Center and have conceded just three goals in nine games overall.Charles Boehm is a contributor to MLSnet.com.