It took a bit longer than expected, but the US Open Cup quarterfinals are finally set, and some clear contenders for the title are starting to emerge.

Though the path to the title may only involve five games for MLS sides (six or seven for lower-league sides), success in the country's oldest soccer tournament is no easy thing. The matches often fall smack in the middle of busy league schedules, especialy during the later stages, when teams are focused on making a playoff push.

POLL: Which of the US Open Cup quarterfinalists has the best shot of winning it all?

To succeed in the Open Cup requires not only a good team, but one capable of battling through adverse conditions that may not be found in MLS play. It calls for a group capable of clawing past defensive-minded lower division squads, and a deep roster.

There are three teams in the remaining 2013 field that jump out as ones that check off all those boxes. Read on to find out who they are, and if you disagree, be sure to tell us why in the comments below and vote in the poll to the right!

Portland Timbers

If one thing's been plainly obvious this season, it's that these are not your 2011-12 Timbers. This team is ambitious, deep, and above all, good, meaning there's no reason they shouldn't be gunning for the Open Cup in addition to a first-ever playoff appearance.

Caleb Porter's men have dispatched two lower league teams with ease, and though they face a much tougher opponent in Western Conference leaders FC Dallas in the quarterfinals, it's an opponent they will be plenty familiar with (they play in the league on Saturday) and a fixture they should be able to handle well.

READ: Michael Nanchoff whacks Tampa Bay Rowdies, Caleb Porter in Timbers win

Porter has done a smart job of mixing his regular starters with players further out on the fringe, a tactic that's worked well for his team due largely to the fact that everyone is buying into his system and the fact that he's built a deep team.

Don't be surprised, though, if you see more and more first-teamers filter into the lineup as the USOC stakes get higher. And as anyone who's watched the Timbers play this year will tell you, that group's ability to press and retain possession is a daunting prospect for any team, and a big reason why Portland may have their hands on the trophy come October.

Real Salt Lake

It was not always smooth sailing for the Claret-and-Cobalt in their fourth-round victory over the stubborn Charleston Battery – who had already knocked off the San Jose Earthquakes – but the ability to claw their way back against an ultra-defensive minded opponent and the depth they showed Wednesday night illustrate why RSL could be in line for their first-ever Open Cup title.

In what was forecast by some as a rebuilding season, though dubbed by the RSL management as a "reload," the team has looked like their old selves, remaining a force in the Western Conference and totaling eight goals in their first two Open Cup games.

There is an incredible depth and variety in RSL's forward line, arguably better than any they've had, while the midfield remains imposing, led by a revitalized Javier Morales. The defense remains shaky at times, as evidenced by the two goals apiece given up to lower league opposition, but given all the other factors it would be hard to bet against one of MLS' most consistent contenders making a play for the Open Cup.

Orlando City

WATCH: Orlando City topple Sporting KC

Can a lower-division team finally recapture the glory the Rochester Raging Rhinos found in 1999? If there's any team built to do it, it's the ambitious Lions.

Think about this: This is a team that just shocked the defending champs and their MLS affiliate in their own home, all while missing the four players they had on loan from Sporting KC. Two of those players were the team co-leaders in minutes played in the USL PRO – Yann Songo'o and Dom Dwyer, with the latter being the runaway Golden Boot leader for Orlando City, talling an incredible 15 goals in 13 games thus far.

READ: Ambitious Orlando City add another MLS notch to their belt after shocking Sporting KC

With their key contributors back and a comparatively kind draw – not to say facing the Chicago Fire at Toyota Park is a cakewalk, but it's not the most difficult quarterfinal assignment they could've picked up – one has to wonder if the Lions will make another statement of their MLS ambition by winning the Open Cup.

They've shown they can defend (0.85 goals against average in USL PRO), they can certainly attack (2.62 goals per game in USL PRO plus a three-goal outing against the Colorado Rapids), they can mix it up with the big boys, and they've got a squad that's crusing through the USL, having built a seven point lead in table. So why not?