Minnesota United are currently promoting their "Summer of Soccer", including friendlies with Swansea City and the Mexico U-21 team. Throw in their league game at TCF Bank Stadium, and it's an important summer for the club from a marketing standpoint - but on the field, the most important game of the summer might be tonight, against Sporting Kansas City in the US Open Cup.

Friendlies are fun, but by the end of the year, it'll be tough to remember whether United won or lost against either Swansea or Mexico's youngsters. And while the game at TCF Bank Stadium will take place on a bigger stage, it's still just a regular league game.

Win tonight, though, and the Portland Timbers come to town next week. Win tonight, and Minnesota will be the team that beat the MLS champions. Win tonight, and the transformation from plucky underdogs - "the team that nobody wanted" - to a force to be reckoned with will be, in some ways, complete.

"It's become even more important because we have a club that expects us to get silverware," said United head coach Manny Lagos. "The US Open Cup means potential credibility at a different level. Teams are taking it particularly seriously, because winning it gives you a spot in the CONCACAF Champions League, which is coveted nowadays."

For Lagos, though, the US Open Cup is no longer about proving yourself. "I feel like that storyline is a couple of years ago," he said. "The guys on the team feel like they should compete against any team in North America right now."

It's that chance to compete that is most exciting for the players on the club. "This is a big one," said defender Justin Davis, who spoke about wanting to prove that NASL teams could beat MLS teams. "KC being geographically close to us, it's one of the bigger games for the club for sure. We're going to go in there like it's a cup final."

Four MLS teams have gone down already. New York lost to their crosstown neighbors, the Cosmos, in a 3-0 beating that had the Red Bulls' fans incensed about coach Mike Petke's cavalier attitude to the competition. Carolina, always tough at home, beat floundering Chivas USA on penalties, and Atlanta won 2-1 against Real Salt Lake, to make a trio of NASL teams already into the fifth round. DC United also lost to third-division Rochester. Seven other MLS teams have already gone through to the next round as well, two of them over NASL sides; Minnesota has a chance to keep the league's winning record against MLS intact.

That said, beating Kansas City is a much taller order; for one, the team is unlikely to throw out a half-strength team. "I know the coaching staff there very well," said Lagos. "They're going to take the game very seriously."

Not only are KC the reigning MLS champions, but they play a high-pressing style that has troubled Minnesota in the past. The Cosmos did the same to Minnesota earlier this year, and United went about the first hour of the game seemingly without completing a pass or putting together anything organized offensively. Sporting is well known for doing the same, and it concerns Lagos, who says he'll have to treat this different than a normal NASL game. "'d be a little naive if I didn't think about it differently, particularly against Kansas City, which has developed a style that's different than some other MLS teams," said the coach. "We're going to have to absorb a different type of tempo than we're used to, a different type of pressing, a different speed of play. I think even teams in MLS have to deal with that when they play Sporting KC."

Both teams will have to deal with the heat, as well; temps will reach the 90s in Kansas City today, and while kickoff isn't until 7:30 - you can see the game on sportingkc.com - it'll still be plenty warm.

It'll be a tall order for United. Whatever the team might say, they are underdogs this evening, on the road in one of America's toughest places to play. If they can come through with a win, the rest of the summer - despite the marquee games - might pale in comparison.