Part of D.C. United's evolutionary process is to go beyond its modest MLS borders and test itself against clubs from long-established leagues.

Exhibitions such as this summer's friendly with English champion Chelsea and frequent participation in modest regional tournaments with Central American and Caribbean teams were the first step. But to truly gauge United's progress -- and MLS's, for that matter -- over 10 unassuming seasons is to play meaningful games against Latin American and European teams.

That's why, amid the hectic final stretch of its regular season, United has turned its attention to the Copa Sudamericana, a 12-nation, 34-team tournament comprising some of the top clubs in South America.

United is paired with Universidad Catolica, the Chilean league leader, which will visit RFK Stadium tonight in the first leg of a round-of-16 series. The finale will take place Sept. 22 in Santiago, Chile, with the winner advancing to face Fluminense of Brazil or Banfield of Argentina in the quarterfinals.

The tournament finalists will earn $795,000 and $695,000 -- extraordinary amounts for thrifty MLS teams.

"It's important for the league, and especially for our club," said team captain Jaime Moreno, a Bolivian forward who has played in MLS since its inception in 1996. "A lot of players were waiting for this opportunity. I think it will be a great experience and hopefully it will open the door for American teams to play more of these kind of games."

United's most recent experience in a serious match against a prestigious Latin club did not go well -- a 5-0 road loss to Pumas of Mexico City in April during the semifinals of a low-key regional event. (The teams had played to a 1-1 tie in the first leg at RFK.)

United was the first U.S. team invited to the Copa Sudamericana, which was established three years ago as a complement to the continent's biggest club competition, the 45-year-old Copa Libertadores.

World renowned Boca Juniors of Buenos Aires is the defending Sudamericana champion. Two Mexican teams were also invited this year.

Although United has faced European clubs many times, its experience against South American teams has been limited to a pair of matches with Brazil's Vasco da Gama in the 1998 Interamerican Cup (won by United on a 2-1 aggregate score) and a 0-0 exhibition against Boca Juniors in 2002.

"We have a bad taste in our mouth after the game against Pumas, but during the [last five] months we really gained experience," Coach Peter Nowak said. "For us, we're not playing every single year in an international competition, so this is a very good experience for our young kids to see a different environment.

"It's a learning process. We just want to make it better for everyone, better for our league and better for our team."

Catolica, established in 1937, is in first place in the Chilean league with a 6-0-2 record, outscoring its opponents 12-0. While United (13-9-5 in MLS) earned a bye to the Copa Sudamericana's round of 16, Catolica needed to defeat Universidad de Chile and Alianza Atletico (Peru) to advance.

Besides Moreno, United has two other starters well-acquainted with South American clubs and their playing styles: Argentines Christian Gomez and Facundo Erpen, both of whom arrived in MLS in the past year.

Nonetheless, "international competition is a lot different," Nowak said. "The referees are different, the environment is different, the players are different. So we'll see how this goes. It's very important, the first game. We want to take advantage of [playing at] home."

Universidad Catolica's Jose Fuenzalida, right, heads into RFK Stadium tonight. D.C. captain Jaime Moreno calls the match "an opportunity."