1 key matchup in each conference semifinal tilt

Eight teams remain in the hunt for the 2017 MLS Cup as the Knockout Round came to a close last week. The focus now shifts toward the MLS Conference Semifinals, where these sides will battle in a home-and-away series for a spot in the penultimate playoff round.

Cascadia is well represented in this final eight, as the Seattle Sounders square off against the Vancouver Whitecaps, while the Portland Timbers take on the Houston Dynamo in the West. Over in the East, Toronto FC has a date with the New York Red Bulls, while New York City FC takes on the Columbus Crew.

Here is one key matchup to watch in each of these two-legged tilts:

Toronto FC vs. NY Red Bulls

On paper, Toronto FC's overwhelming offense and steadfast defense presents problems for the Red Bulls across the park, particularly in the backline as Jozy Altidore and Sebastian Giovinco combine to part the gates. But the key matchup here might be how 24-year-old Sean Davis handles the trickery and imagination of Victor Vazquez in the middle of the park.

Michael Bradley should handle the reverse of this battle and limit Sacha Kljestan's influence in the middle of the park, but it will take a bit more for Davis and his midfield partner Felipe to keep an eye on the Spaniard as he slips between lines and delivers cutting through passes. With TFC's dynamic duo up top spreading the backline, Davis has a lot on his plate defensively.

NYCFC vs. Columbus

So much of the Columbus Crew's attack flows through Federico Higuain that it would be easy to identify him as the core problem and subsequently call upon Alexander Ring as the key match to the Argentine's influence. But the bigger battle will be how the Crew defense handles David Villa and Maxi Moralez.

It took penalties to get Columbus to this spot, but Gregg Berhalter's backline did an admirable job keeping Atlanta United's attacking duo of Miguel Almiron and Josef Martinez off the scoresheet. Perhaps Villa and Moralez will see a similar stonewall approach, but can the Crew keep them out over two legs? Crew center-back Jonathan Mensah didn't look entirely solid through the entire 120 minutes, after all - but goalkeeper Zack Steffen certainly did.

Seattle vs. Vancouver

Sans Clint Dempsey due to a red card suspension, the Seattle Sounders will have quite the task on their hands breaking down the door of a resolute rival in the Vancouver Whitecaps, but keep an eye out for the wide battle in this series. Both teams are built to play through the middle, fueled by attacking players who like to cut in to create chances. As such, there's lots of space out wide to exploit.

Jordan Morris has not yet fully recovered from a hamstring injury he picked up in September, so the impetus falls on Harry Shipp as he tries to slip in between Tony Tchani and Marcel de Jong on the right flank. Nicolas Lodeiro will likely slot into Dempsey's open No. 10 role, and with him in the middle, Shipp can do a lot of damage utilizing his penchant for well-hit crosses or shots from distance.

Portland vs. Houston

The Portland Timbers owe quite a bit this year to the work and talent of Diego Valeri but he isn't necessarily the main character in this clash. The Houston Dynamo have plenty of bodies in midfield to keep an eye on Valeri, at the very least. But the Dynamo's backline lacks pace, a delicious prospect for Timbers winger Sebastian Blanco.

Consider the following: the Dynamo started Philippe Senderos in their last tilt, and while the Swiss center-back has a lot of experience, he doesn't quite have the pace to keep up with the wily Argentine winger. Luckily, Adolfo Machado filled in quite nicely at right-back in A.J. DeLaGarza's absence against Sporting Kansas City, and if Machado is called upon again, Blanco might have a bit more of a task on his hands.

(Photos courtesy: Action Images)