WASHINGTON, DC -- D.C. United's league match against Houston Dynamo at RFK Stadium on Saturday night brings together two of Major League Soccer's most successful clubs, a duo which can claim six MLS Cup trophies between them.But the evening will kick off with the home club playing host to an even more luminous guest, as United's under-16 academy squad takes on their counterparts from Spanish giant Real Madrid C.F. in the opening match of the Tiffany Trophy Cup at 4:30 p.m. ET.The weeklong tournament pits several of the Washington region's top youth teams against a star-studded array of foreign visitors. Real Madrid, whose historic nine European Cups and 31 Spanish Primera Liga titles have made them one of the world's most recognized and respected clubs, are the leading entry on an impressive list of overseas guests which also includes youngsters from English Premier League side Blackburn Rovers FC, Mexican legends Chivas de Guadalajara and Costa Rican powerhouse Deportivo Saprissa."These games are actually the most important games for me, as a director, because you get to see really where your kids stand," said John Maessner, United's director of youth development. "We do very well against American teams and we've been able to do decent against top international teams. But still, it's a huge test for our kids to play against guys like Real Madrid, Saprissa ... it just pushes our kids and gives us a good measure of where we're at."Most the boys who will represent United in the Tiffany Trophy Cup fall under the 1992 birth year classification, though Maessner says several younger players -- including one born in 1995 -- will also take part. Many also participated in the "Quixote Trofeo" U-17 Clubs Youth World Cup in Spain last summer, where Maessner's side held their own against top-flight competition like Sevilla FC, Barcelona-based side Espanyol and Serbian outfit FK Partizan.The same squad also took on England's Chelsea Football Academy in a Christmastime showcase tourney at Disney's Wide World of Sports Complex in Orlando, Florida last year. But walking onto the RFK Stadium turf to face the youth representatives from the most successful club in European history will present an unparalleled test for the Black-and-Red -- not only physically, but mentally as well."It's natural to get nervous, but it's also good for them to experience that and then be able to get through it. So the experience is going to be great, it's going to be awesome for our kids," said Maessner. "The Real Madrid kids, I already know they won't be nervous. They're just going to play, just like the Chelsea kids played in Disney, when we were a little bit nervous in the first half."The European kids, the South American kids, when they have a big game they just play like they play every day, and that's where we want to get our kids. So psychologically it's very interesting."Maessner will be able to call on Julio Arjona and Shaquille Phillips, two United Academy standouts who joined the U.S. Soccer residency program in Bradenton, Fla. earlier this year, but returned to D.C. on Tuesday to take part in this tournament. Arjona cites United, Liverpool FC and Real Madrid as his favorite international clubs and is eager to face off against Los Merengues (a nickname derived from their famous all-white uniform) on Saturday."It's good for American teams, clubs around here, to see how the competition is in Europe, so we can compare ourselves with teams in Europe to see how good we are," said the defender from Germantown, Md. "I think this cup is a really good chance to prove that we've got some skill in America, that we know what we're doing."Maessner was able to watch Madrid's U-17 side in Quixote Trofeo last year and was mightily impressed. The D.C. academy is in relative infancy compared to such well-established clubs, but his program has already begun to churn out NCAA Division I-worthy prospects and he feels confident that it will begin providing United's senior squad with talent in the next few years."We've been preparing our kids to just go out and play. It's a soccer game -- we're playing Real Madrid, one of the biggest clubs in the world, but it's still just a soccer game and they're still just 17 years old like we are," said Maessner of Saturday's clash. "So we hope that our kids just go out and show up and play. If they do that and they're confident, I think we have a chance to beat anybody we play against, like we did in Spain last year."