With at least 90 minutes left to play in the MLS Eastern and Western Conference finals, both of the top seeds are facing deficits.

FC Dallas, who earned the No. 1 seed in the West, scored a key away goal in the first leg, but they are down 3-1 to the Portland Timbers. The New York Red Bulls, who are the No. 1 seed in the East, failed to find the back of the net on their travels and conceded twice to the Columbus Crew. Now with two spots in the MLS Cup final and the potential to host the championship match on the line, both top seeds must find a way to rebound from the first leg.

The formula seems simple for FC Dallas in the first match on Sunday since they are the owners of the best regular-season home record. However, Portland tied for the league lead in road wins and hasn't lost on the road since August.

In order to reach the club's first MLS Cup final since 2010, Oscar Pareja's side must receive more out of the attack-minded players in the starting XI.

Mauro Diaz shone a bit in the first leg, but when he had chances to finish off an away goal on set pieces, he failed to put a shot on target. Fabian Castillo and Michael Barrios were marked out of the match by Portland's full backs, Alvas Powell and Jorge Villafana, which cut off most of the supply lines to forward David Texeira. But in a strange development, Texeira netted his first goal of the postseason while Portland realigned its defense following the departure of Liam Ridgewell.

FC Dallas must use the first leg as a learning experience and find a way to adjust to Portland's defensive scheme. Castillo found a few gaps against Powell, but for the most part, he did not make an impact. If the dynamic Colombian begins the match with a few superb runs, it will give him time to set up Diaz in the middle of the field. 

If Castillo gets going on the left wing, he will also up the potential for overlapping runs from Ryan Hollingshead, which could cause a good bit of trouble to the Portland back line. But the real key, as it has been for most of the postseason, is the form of Texeira up top. If the Uruguayan uses his first-leg goal as a springboard into the second leg, FC Dallas could finally have a complete set of in-form attackers. If Texeira fails to show up, we may see Blas Perez or Tesho Akindele make an early entrance. 

As for Portland, it all of a sudden has an embarrassment of riches moving forward, with both Diego Valeri and Rodney Wallace returning from suspension. Because of the terrific first-leg performance put in by Dairon Asprilla on the wing, Timbers boss Caleb Porter may have a tough time deciding who starts alongside Darlington Nagbe on Sunday.

Regardless of who finds their way into the Portland starting XI, they must be able to strike on the counter early in a game wherein FC Dallas are expected to dictate the pace. An early away goal would most likely sink the fate of the home side and put Portland into its first MLS Cup final. 

A goal in the first 20 minutes would most likely come from Nagbe, who is flowing with confidence in the final third. Adding Valeri to the attack will allow Nagbe to have more freedom as he searches for space in the FC Dallas defense. Even if Portland records an early tally, do not expect the Timbers to sit back and defend. Portland will push for more goals, which means we could witness a wide-open affair at Toyota Stadium.

The focus will be on the Red Bulls attack in Sunday's second game as the hosts try to pull back a pair of goals at Red Bull Arena. Just like FC Dallas, the Red Bulls could not get a sufficient attack going in the first leg because of the play of the opposing full backs. Lloyd Sam and Mike Grella had little impact on the game, which meant Bradley Wright-Phillips did not receive any quality service. 

The biggest surprise in the first leg for Jesse Marsch's side was the poor play of Dax McCarty and Sacha Kljestan in central midfield. Both players looked disjointed, and that led to Columbus' duo of Wil Trapp and Tony Tchani dominating the middle of the park. With the potential to host the MLS Cup final on the line, expect McCarty and Kljestan to succeed. But if they don't produce any goals, their respective performances could be all for naught.

Columbus comes into the second leg with a comfortable advantage, but the Crew also wasted some chances at home in the first leg. In order for those missed opportunities not to come back and haunt them, the Crew must find a way to get Ethan Finlay and Kei Kamara involved from the first whistle. If the dangerous attacking duo creates chances in the first 20 minutes, it will force the Red Bulls full backs to remain deep and not charge forward in search of scoring moves of their own. 

As always, Kamara's aerial ability could be a major factor in determining the final result. All it takes is one leap and one solid cross from the wing for the Crew to find the back of the net through the Sierra Leone international. On the topic of service, Federico Higuain must be more direct when he has the ball at his feet. On too many occasions in the first leg, Higuain decided to dance around and be cute in the final third instead of surging toward goal.

All four clubs still have a chance to get through to the final, but each faces a special set of circumstances. With that in mind, we'll take Columbus at FC Dallas in the MLS Cup final. 

Conference Final 2nd-Leg Schedule

Portland Timbers at FC Dallas (Sunday, 5 p.m., ESPN)

Columbus Crew at New York Red Bulls (Sunday, 7:30 p.m., Fox Sports 1) 

Players to Watch

Diego Chara, CDM, Portland Timbers

Midfield enforcer Diego Chara of the Portland Timbers must shut down Diaz for the second straight week in order for Portland to reach its first MLS Cup final. 

Chara played Diaz physically in the first leg, but he must be clean and not earn a yellow like he did last time out.

There is no doubt the battle between Chara and Diaz will be at the forefront of the Western Conference Final second leg, but if Chara gets booked early, he may be forced to back off, which could open up room for Diaz to shine.

Fabian Castillo, LM, FC Dallas

Against arguably the best right back in the league in the first leg, Fabian Castillo failed to light a spark in the FC Dallas attack for 90 minutes.

But now that he's on home soil and with the possibility of his team hosting the MLS Cup final looking him in the face, expect the Colombian to have his way with Powell, at least in the early going in Texas. 

Scoring the first goal will be crucial on Sunday in Frisco. If FC Dallas strike first, they will able to take advantage of their away tally. But if Castillo fails to open up the Portland back line, the Timbers may be able to score an away strike of their own. 

Gaston Sauro, CB, Columbus Crew

Gaston Sauro returns to the field after a one-game suspension with a major task on his hands. The summer acquisition must limit the opportunities Wright-Phillips receives in the box. 

If the Argentinian center back keeps Wright-Phillips quiet for 90 minutes, he will force the Red Bulls midfielders to get creative. Based off the first-leg showing by the Crew full backs, that could be a winning formula for Gregg Berhalter's side. 

Lloyd Sam and Mike Grella, AM, New York Red Bulls

Sam and Grella simply must be better than they were in the first leg in Columbus. Both of the Red Bulls wingers failed to make any type of positive impact on the team's attack at Mapfre Stadium. 

There are ways to exploit space against the Crew full backs, but neither player found a way past Harrison Afful or Waylon Francis in the first leg.

If they fail to settle into the second leg, look for them to switch sides in attack. If that doesn't work, we could be seeing an early substitution from Marsch. 

Joe Tansey covers MLS for Bleacher Report. You can follow him on Twitter, @JTansey90. 

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