Leading off with a spoiler is probably not a great idea, but the fact that D.C. United will face virtually the exact same New York Red Bulls starting lineup today is unavoidable. Jesse Marsch settled on his ideal front six months ago, along with half of his defense. In goal, Luis Robles hasn't missed an MLS match since 2012. Once the MLS Disciplinary Committee decided violent, dangerous conduct does not merit further punishment, the NYRB starters were essentially set in stone.
That means the 4231 will once again be in effect:
Robles was not tested at RFK in terms of shots on goal, but on crosses he seemed a little hesitant more than once. That's good news for United, since in all likelihood they'll be looking to pump crosses into the box for Alvaro Saborio. United needs to make sure Robles pays for things like staying on his line because he doesn't have the strength to barrel out and claim crosses in traffic.
Sal Sizzo has 6 straight starts over Connor Lade, so any questions about which player Marsch prefers can be put to bed. Zizzo had 3 key passes last week, overshadowing Lloyd Sam - who normally kills United - down the right flank. With Chris Rolfe likely back on the left wing again, United is going to have to force Zizzo to defend. Remember, Zizzo's previous MLS career had seen him play as an out-and-out winger who only filled in at right back as an emergency. For the Red Bulls, his attacking instincts fit the gameplan. United needs to disrupt all that by finding Rolfe and/or Fabian Espindola along their left side, because Zizzo is not actually comfortable about the defending part of playing as a defender.
In central defense, Matt Miazga has been first-choice for virtually the entire season, and rightly so. However, it's worth noting that it was his marking that was at fault when Alvaro Saborio wasted United's best chance of the match by heading Espindola's cross over midway through the first half. Saborio can bully Miazga - who at 20 has yet to really fill out his frame - and he should absolutely look to antagonize him. Miazga can't help himself when it comes to arguing with referees and jumping into on-field disputes; his default setting is to be a little too pissed off about whatever is going on, no matter how minor. This is a battle Sabo can win both mentally and physically, and he pretty much has to if United is going to turn this one around.
Ronald Zubar will start for the injured Damien Perrinelle, who it turns out tore his ACL in an awkward landing early in the second half at RFK. Zubar almost immediately ran into Miazga going for a harmless ball in the air, and later absolutely - again, absolutely - should have been sent off for launching himself at Markus Halsti about 17 minutes later. Zubar has looked prone to weird mistakes borne of a lack of communication all season, which is an odd problem for a player who has played in Ligue 1 and the Premier League. It's not so much that he can't communicate that he simply doesn't appear to do so, or to listen to others. If there's a player Espindola can torch like he did Andrew Farrell in the knockout round, Zubar is the guy to target.
Kemar Lawrence is an attacking menace from left back thanks to his speed and sheer persistence. Despite being quiet by his standards in the first leg, his starting point - despite playing as a fullback, 10 of his 17 completed passes in the first leg originated in United's half - is still so aggressive that it causes problems. United's long ball play failed in part because the wide midfielders had to be cautious due to Lawrence and Zizzo, and that's a problem that won't go away until DCU exploits the space in behind either of them enough times to force Marsch to make them play more conservatively. If United is taking steps to avoid being pinned into their own end, Lawrence's positioning will be a good bellwether.
Dax McCarty, Felipe, and Sacha Kljestan will continue as the central midfield triangle. As always, it's the combination of their fluid movement and their dynamic nature that makes them so hard to deal with. None of the three is the most skillful player in MLS that plays their roles; they're just really good at making the game easy for themselves.
The key here is being more aggressive towards McCarty and preventing him from connecting so many passes so easily. McCarty misplaced just 9 passes in the first leg, 8 of which were attack-minded vertical balls. United needs to make McCarty connect less often and to generally force NYRB to focus their passing out of the back elsewhere. With Felipe preferring to drift ahead of McCarty in possession and then play off of the former United and FC Dallas man, it might help United to cheat a bit and allow those more demanding passes to Felipe in exchange for making it harder to find McCarty.
Sam remains a big problem for United, even when he wasn't able to provide much of a goal or assist threat in the first leg. Taylor Kemp has to give up so much to cope with Sam that guys like Kljestan and Zizzo are getting free between the lines in the areas Kemp can't step into. Look for Sam to stay wide and keep forcing this to happen, while also stepping high to restrict Kemp's ability to attack. It would make plenty of sense to play Nick DeLeon at left midfield in this one to help out, but he may be at right back due to Sean Franklin's questionable status.
On the other wing, Mike Grella is looking for chances to run at defenders and get into the box to go to goal. The converted striker is less of a set-up man and more of a goal-dangerous winger these days, and with NYRB trying to attack Kemp it means that someone always needs to be tracking his back post runs. Grella's role in this attack is to be the man who gets forgotten about and then punishes teams for doing so.
Bradley Wright-Phillips remains a well-rounded attacking threat as the lone striker. He proved he can be an elite goal-poacher in the Thierry Henry days, but this year he's shown a lot more in terms of contributing in the build-up and creating for others. His ability to combine at the top of the box has become a major factor for the NYRB attack, and tracking him in those situations is critical.
Off the bench, Perrinelle's injury has robbed Marsch of one option he's used sporadically this year: The move to a 541, with Zubar coming in to help combat a late bombardment of crosses. Karl Ouimette is not as good in the air as Zubar, so I have my doubts about Marsch going for that move if we're still looking at a tied game after the 85th minute. Gonzalo Veron appears to be the first winger off the bench these days, though he doesn't really look that comfortable playing as a winger yet in MLS. Lade could come in for Zizzo as a more conservative option at left back, while we could also see Felipe replaced by Sean Davis if the Red Bulls are thinking of becoming more defensive. Shaun Wright-Phillips is also a candidate to step in, though at 34 his game is more about guile than the speed that he was originally known for.