Major League Soccer entered the conference semifinal phase of the MLS Cup playoffs on Sunday, with the eight remaining teams looking to get an advantage in the first of the two-legged ties.

D.C. United and the New York Red Bulls met in the first of two Eastern Conference clashes followed by the Columbus Crew and Montreal Impact later in the evening.

Over in the Western Conference, the Vancouver Whitecaps and Portland Timbers renewed their rivalry, while the Seattle Sounders were hoping FC Dallas wouldn't derail their hopes of winning an MLS Cup for the first time.

Here's a look at how Sunday's matches unfolded.

The Eastern Conference's top seed drew first blood in the conference semifinals after Dax McCarty's goal in the 72nd minute gave the New York Red Bulls a 1-0 win over D.C. United on the road in RFK Stadium.

Sacha Kljestan picked up the assist, as his right-footed delivery on a set piece found McCarty on the edge of the six-yard box, per MLS:

Some D.C. United supporters will feel wronged by referee Fotis Bazakos after Ronald Zubar escaped a red card in the 69th minute. The Red Bulls defender took out Markus Halsti with a late tackle, and MLSSoccer.com's Andrew Wiebe was among those calling for Zubar's dismissal:

Instead, the match official allowed Zubar to stay on the pitch.

D.C. United coach Ben Olsen disagreed with the decision.

"It has all of the ingredients of what they've been saying is a red card in this league," Olsen said after the match, per Goal's Thomas Floyd.

Even taking into account the Zubar yellow, D.C. United only have themselves to blame for the result. Despite playing in front of a home crowd, they offered little in the way of an attack. According to MLSSoccer.com, Olsen's side completed just 40 percent of its passes in the final third and failed to register a shot on target.

Howler Magazine offered a visualization of D.C. United's buildup play:

The Red Bulls undoubtedly control the tie now. Not only do they have a 1-0 advantage after the first leg, but their away goal means D.C. needs to score at least twice in normal time at Red Bull Arena to progress to the conference final if it wants to avoid extra time and penalties.

In addition, D.C. United took only 15 out of a possible 51 points away from home—third fewest in the Eastern Conference.

Nothing separated the Portland Timbers and Vancouver Whitecaps on Sunday, as the two sides played to a 0-0 draw.

In their knockout-round victory over Sporting Kansas City, the Timbers benefited from the goal itself, as a Saad Abdul-Salaam attempt hit both posts before bouncing away from goal in the penalty shootout. As a result, Portland stayed alive.

The Timbers' luck turned around against Vancouver.

In the 89th minute, Maxi Urruti had Sporting KC goalkeeper David Ousted beat with a right-footed shot at the far post. Already wheeling away in celebration, Urruti watched as the ball deflected off the right post and away from danger.

Abdul-Salaam showed off his sense of humor following Urruti's miss:

Diego Valeri nearly gave Portland a 1-0 lead 18 minutes earlier after his free kick toward the top corner was knocked away by Ousted, per MLS:

Although the Timbers would have liked to pick up a win at home Sunday, a scoreless draw isn't the worst result they could've experienced. They didn't concede an away goal, which could be crucial in the second leg.

Plus, Portland is a very good road team, picking up 23 points in its 17 matches away from Providence Park in the regular season.

Patrice Bernier canceled out Federico Higuain's goal in the 37th minute, and Johan Venegas delivered the winner in the 77th minute to put the Montreal Impact up 2-1 after their first-leg clash with Columbus Crew.

Higuian gave the Crew an early lead after Didier Drogba delivered a perfect assist to the Argentinian forward. Too bad Drogba plays for the Impact, per MLS:

Another bit of horrendous set-piece defending followed, this time courtesy of the Crew. Columbus left Bernier completely unmarked on a corner, and he placed his header into the back of the net.

Poor defending was a hallmark for the Crew earlier in the year, and supporters must have had flashbacks after center back Michael Parkhurst gifted Venegas the Impact's second goal.

Parkhurst lost possession to Venegas in midfield, which allowed the Costa Rican a free run at goal. He had Drogba to his right but opted to take the shot himself and promptly scored:

MLSSoccer.com's Matthew Doyle thought Venegas opened himself up to a lot of potential criticism by not passing the ball off to Drogba, who would've had a simple finish:

Gregg Berhalter's side controlled possession for much of the game but demonstrated possession alone doesn't equate to goals. Columbus completed 83 percent of its passes, including a healthy 69 percent in the final third, per MLSSoccer.com.

The Crew couldn't translate all of that passing into genuine goalscoring opportunities, however, getting just three shots on target and only recording six shots in total.

Columbus needs to be much more efficient with its attacking moves in the second leg or it risks an early exit from the playoffs.

The No. 2 seed in the Eastern Conference might receive a boost in the coming days, however.

For the second time in the day, the officials became part of the story after failing to send off a player for what could've been a red card-worthy offense.

In the 87th minute, Drogba received a yellow card for a foul on Crew goalkeeper Steve Clark. Either referee Chris Penso and his assistants missed Drogba grabbing Clark's leg or deemed a sending-off too harsh a punishment. Whatever the reasoning, it made for a ridiculous visual, per Sports Illustrated's Planet Futbol:

If MLS retroactively punishes Drogba, his absence would be a massive blow to the Impact in the second leg. The Ivorian striker has arguably been Montreal's best player since his arrival in the summer.

Clint Dempsey, Seattle hero.

The Seattle Sounders superstar played the role of game-winner during his team’s 2-1 victory over FC Dallas in the opening leg of the second Western Conference semifinal on Sunday. He drilled the clinching shot into the upper right of the goal down the stretch to break the tie at the 86th minute. 

It sent the crowd into a frenzy and put the Sounders in control of the matchup. The team passed along the highlight:

While Dempsey put home what proved to be the game-winning goal, it was FC Dallas that jumped on top in the first half. Fabian Castillo opened the scoring in the 18th minute, and the Sounders were facing a deficit in a critical contest at home.

That hole wasn’t a problem for Seattle, as coach Sigi Schmid explained, per the team’s Twitter account: "We're a team that believes...that one-goal lead wasn't going to deter us. The group...they're willing to do anything right now to help us win. They know it's playoff time and they've really stepped up."

Schmid was right, and Andreas Ivanschitz tied the game in the 67th minute with an unassisted goal to seize the momentum. From there, the Sounders created the opportunity for Dempsey down the stretch and escaped the home leg with the win.

It wasn’t the only victory for the Emerald City in a battle with Dallas on Sunday. The Seattle Seahawks beat the Dallas Cowboys and shared their thoughts on the Sounders’ win in the aftermath of both games:

Advantage Seattle.

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