Philadelphia Union vs DC United
The Union and DC United have split two meetings this year with the Union taking the first 1-0 on May 17th and United rallying for a 2-1 win two weeks later. Neither side won in regulation in Round 4 with the Union being held scoreless for 120 minutes and requiring a shootout to get past Rochester, and United scoring twice in added time to defeat the Pittsburgh Riverhounds 3-1. In 2013 these two sides faced off in the fourth round with United walking away with a 3-1 win on the strength of a Dwayne De Rosario hat trick, but the Union have had the more recent Open Cup success as they reached the finals of last year's tournament before falling to Seattle 3-1 in added time.
New York Red Bulls vs New York Cosmos (NASL)
The Cosmos look to bounce the Red Bulls from the Open Cup for a second consecutive season after humiliating them 3-0 a year ago behind two goals from Norwegian striker Mads Stokkelien. The upset-minded Cosmos already have a taste of beating MLS clubs this year as well after rallying from a 2-0 deficit to shock New York City FC. The Red Bulls were no slouches in round 4 either though as they cruised to a 3-0 win over the Atlanta Silverbacks, but lost midfielder Lloyd Sam to an injury in the process.
Chicago Fire vs Charlotte Independence (USL)
Not exactly sure why Dallas and Houston aren't in the South Bracket and Chicago and Columbus aren't in the Central, but I'm sure whoever the geographically savvy person was who came up with this had a good reason. Anyhow, the Independence are the lone USL squad to reach the Round of 16 after pulling off a 1-0 upset of a short-handed New England Revolution club. While clearly the underdogs, the Independence will take on a Fire team that aren't exactly world beaters either. Chicago needed 116 minutes to break through against Louisville City FC in their 1-0 win.
Orlando City SC vs Columbus Crew
The Crew got a big boost from Adam Bedell who notched a brace in his first match of 2015 while Ethan Finlay added a goal of his own in their 3-1 win over the Richmond Kickers. Orlando meanwhile was the beneficiary of three penalty kicks, all of them scored by Carlos Rivas, and still managed to blow a 4-2 lead before winning a ten-round penalty kick shootout 8-7 (during which Rivas ironically missed). In two matches against Orlando this season, Columbus has scored five goals, winning 3-0 and drawing 2-2.
Houston Dynamo vs Colorado Rapids
The Rapids and Dynamo tied 0-0 in their only match-up this season, but the Dynamo have been playing much better as of late thanks to the tandem of Will Bruin and Giles Barnes. The Rapids got a big boost this week from Naval Academy graduate Joseph Greenspan who scored in his Rapids debut and helped them to a 4-1 win over the Colorado Springs Switchbacks. Both clubs lost in the 5th round of last year's tournament and neither side has reached the tournament quarterfinals since Houston did so in 2010.
Sporting Kansas City vs FC Dallas
Dallas broke out of its offensive slump thanks to braces from David Texeira and Micael Barrios against Oklahoma City, but they'll have a much tougher task ahead of them when they face Sporting Kansas City. Sporting routed Dallas 4-0 just three weeks ago atoning for an earlier 3-1 loss back when Dallas was actually playing well. Dallas has not raised the Cup since 1997 while Kansas City won in 2004 and again in 2012.
Real Salt Lake vs Portland Timbers
This match features two clubs going in opposite directions. Real Salt Lake has won just two of their last eleven MLS matches (2-5-3) while Portland is in the midst of the longest winning streak in the history of their franchise. Not to mention that the Timbers just knocked their chief rivals, Seattle, out of the U.S. Open Cup. These two teams met on opening weekend and played to a 0-0 tie.
San Jose Earthquakes vs LA Galaxy
The San Jose Wondos get ready to face off against the Galaxy in the latest installation of the California Clásico. Both of these teams leaned heavily on their stars in Round 4 as Chris Wondolowski put the Quakes on his back and rallied them from a 2-0 deficit to knock off the Sacramento Republic while Robbie Keane picked up a hat trick in LA's 6-1 win over lower division side PSA Elite. The two clubs haven't faced each other yet this season, but LA won the season series a year ago with a win and two draws. Wondo scored a pair against LA last season.