By Tuesday night's end, the U.S. Open Cup field will be down to four teams.
A three-time defending champion, four other MLS sides and three upstart USL Pro clubs remain in what has been a riveting tournament so far under the new format.
The two big questions looming Tuesday are: Will the Sounders' Open Cup reign finally come to an end against an in-form San Jose side? In a tournament full of Cinderella stories, will any USL Pro clubs make it to the semifinals?
Here is a closer look at the night's four matches along with the pairings for the semifinal round:
U.S. OPEN CUP QUARTERFINALS
PHILADELPHIA UNION vs. HARRISBURG CITY ISLANDERS (7:30 p.m.)
It's essentially Big Brother vs. Little Brother, as the Union take on their affiliate club for the second time in two weeks after dropping a 3-2 friendly result to the City Islanders on June 12.
The Union are playing a much more inspired, confident attacking game under interim coach John Hackworth and are coming off a 4-0 thrashing of Sporting Kansas City Saturday to build some momentum heading into Tuesday night's match.
The City Islanders have been an MLS killing machine this tournament, taking down the New England Revolution in penalty kicks after one of the wildest periods of extra time ever and the New York Red Bulls in the following round in extra time to reach the quarterfinals. Both of those matches were at home, however, where the City Islanders are unbeaten against MLS competition. Venturing into PPL Park against a motivated Union side will be another challenge altogether.
SPORTING KANSAS CITY vs. DAYTON DUTCH LIONS (8:30 p.m.)
It's hard to know what to make of the Dutch Lions, who are the Toronto FC of this tournament field in that they just won their first league game (1-7-5 in USL Pro) while finding success in non-league competitions. Their most pronounced victory came over the Columbus Crew in the third round, and they topped Cinderella PDL side Michigan Bucks to keep their run alive.
They'll meet a Sporting Kansas City side that has had its high ups be met with some recent low downs, most notably the weekend loss in Philadephia. With SKC returning to Livestrong Sporting Park for this match, it would seem like the ideal way to turn things around ahead of Friday night's nationally televised league match against the Chicago Fire.
CHIVAS USA vs. CHARLOTTE EAGLES (10:30 p.m.)
Chivas have quietly marched on in this tournament, taking care of the Ventura County Fusion and Carolina RailHawks in professional, yet unspectacular fashion, leaving them as a potential dark horse MLS side and one with a golden path to the semifinals.
In their way stand the Eagles. With another win, Charlotte would have one more Open Cup win than it does in USL Pro play this season. The club deserves credit for getting by FC Dallas and the San Antonio Scorpions, but heading cross country to Titan Stadium in Fullerton, Calif., is no easy proposition.
"It is kind of strange that we can't win in the league, but we're going through the Open Cup," Charlotte coach Mark Steffens told U.S. Soccer's official website. "This is a hardworking group. We have veterans who have been around for a while and we’ve got some talented young kids. We’ve got a good mixture and a great dynamic. There is a unity on this squad and the guys genuinely like each other. I think that goes a long way."
SAN JOSE EARTHQUAKES vs. SEATTLE SOUNDERS (10:30 p.m.)
The Sounders, winless in seven MLS games, enter the match just having played an intense rivalry match in Portland on Sunday, meaning that Sigi Schmid will likely have to get creative when putting together his lineup.
San Jose, meanwhile, enters with loads of confidence. Coming off a Rocky Mountain road sweep of the Colorado Rapids and Real Salt Lake, the Earthquakes sit atop the Western Conference standings. Frank Yallop will have to be mindful of his lineup selection as well, with a massive rivalry game against the Los Angeles Galaxy looming on Saturday night, but the Earthquakes have proven to be one of the deeper teams in all of MLS.
The odds would appear to be against the Sounders in this tournament for the first time in about three years. Considering the current forms of both teams, the fact that this match will be hosted by San Jose and compound that with the little rest the Sounders will have had, Tuesday night could very well mark the end of a tremendous Open Cup reign. The tournament means plenty to Seattle though, and it would be unwise to count out the champions before the final whistle is blown at Kezar Stadium in San Francisco.
"This is probably our most difficult challenge, having to come back and play on just one day’s rest against a team that has two days of rest," Schmid told SoundersFC.com. "It is what it is. It’s a challenge we have to accept, and we have to rise up to it."
U.S. OPEN CUP SEMIFINAL PAIRINGS (games either July 10 or 11)
Sporting Kansas City/Dayton Dutch Lions at Philadelphia Union
Harrisburg City Islanders at Sporting Kansas City
Dayton Dutch Lions at Harrisburg City Islanders
Chivas USA/Charlotte Eagles at Seattle Sounders or San Jose Earthquakes
Which teams do you think will win tonight's matches? Is this the night that Seattle's Open Cup run comes to an end? Do you see any of the USL Pro teams continuing on to the semifinals?
Share your thoughts below.