By Charles Boehm / MLSnet.com StaffWASHINGTON -- It's not often that a team has to prove itself worthy to participate in a tournament that it's just won. Yet that is the strange situation facing D.C. United this week as they play host to FC Dallas for a U.S. Open Cup play-in match at RFK Stadium on Wednesday night, despite that fact that the Black-and-Red are the tourney's defending champions."I'm still shocked at how you win it and you don't get a berth into the final round," said midfielder Ben Olsen on Tuesday. "But it's always about building a bigger case for trophies at this club. As disappointing as last year was, we still managed to hold something up and the guys did a great job in that tournament."United won the Open Cup in their 1996 inaugural season, though in many subsequent years it declined in importance as the club's ambitions were focused elsewhere. Thanks to SuperLiga, league play and a barrage of injuries, the midsummer onset of Open Cup play again arrived at an awkward time for D.C. last season, prompting head coach Tom Soehn to field a reserve-heavy lineup.But the United youngsters put together a surprising run in the 96-year-old competition, eventually culminating in a 2-1 cup final victory over the Charleston Battery at RFK on Sept. 3 that constituted the only bright spot in an otherwise dismal campaign. Under the Open Cup's present format for MLS qualification, missing out on last year's MLS Cup Playoffs automatically forces D.C. to progress through two additional rounds of qualification to formally enter this year's version."Any time that you win a tournament, you always want to prove the following year that you can defend it, you can have an opportunity to win it again," said defender Bryan Namoff. "But to not actually be in it yet is a frustrating piece for us."Nonetheless, last season's success has helped stoke higher expectations in 2009, especially given that the improved roster depth at Soehn's disposal has made any and all playing time a commodity."There's a mentality that in the past we went into the Open Cup and we haven't done well because of the leadup to the game: it's such a big dropoff and guys aren't as motivated because they know it's Open Cup," said Santino Quaranta."But I think now people are fighting for positions in the regular season, so this game is a chance for certain guys that haven't been playing to do well. I think that winning it last year does put a little bit of an extra burden because we've done well last year and we expect to do well again."Quaranta missed the first few weeks of the season with a hamstring strain, so he's one of many who are eager to log as many minutes of game action as possible. Soehn's starting lineup against FCD will likely blend veterans like him with several newcomers who have been making a strong case for themselves on the training ground."Obviously we are treating it like it's a must-win situation," said the third-year boss, who helped the Dallas Burn defeat United in the 1997 Open Cup final during his own playing career. "We want to represent Open Cup the best we can and also figure on getting some guys some minutes that have deserved some, and some rest for others. So we're going to manage that accordingly."Playmaker Christian Gomez will miss out due to a hamstring injury sustained against New England on Friday, and while holding midfielder Clyde Simms has recovered from the illness that limited him to 45 minutes that night, on Wednesday he might be spelled by his understudy, Andrew Jacobson. Soehn also hinted at possibly handing an opportunity to one of his backup goalkeepers, Josh Wicks or rookie Milos Kocic, in place of incumbent Louis Crayton."It's going to be a mixture of some of the older guys and younger guys, but it's not too much of a drop-off around here," said Quaranta. "There's some quality players. We're looking to win, obviously, that's number one, and guys want to play, too."