The storylines that will make Decision Day one of MLS' most memorable

When MLS kicked off in March, there were a plenty of uncertainties. The defending champion Seattle Sounders would need to find a way to reincorporate Clint Dempsey. Despite bringing in Juninho and Dax McCarty, the Chicago Fire seemed a piece or two short of truly making noise in the East. On paper, the season seemed to pit FC Dallas and Toronto FC on a collision course to MLS Cup 2017.

Since then, we've seen seismic shifts across the league. While it did take Seattle a while to jell, the Sounders find themselves poised for at least one home match in these upcoming playoffs. The Fire added German lynchpin Bastian Schweinsteiger to form MLS' best midfield. And while Toronto has dominated the regular season, Dallas has endured a historic swoon that finds them on the brink of missing the postseason entirely.

With the season culminating this Sunday, in what stands to be a truly memorable Decision Day, here are four storylines to keep an eye on:

How the West will be won

Last weekend, the Vancouver Whitecaps were just 15 minutes away from clinching the top spot in the Western Conference. For a team that finished eighth last year, it would've been a major statement to top the table in a home match. Instead, visiting San Jose equalized as Vako's chip found its way to the far post and the 'Caps had to wait another week.

Now, the Canadian side will head to Providence Park with everything on the line. Whoever can find a way to win between Vancouver and the hosting Portland Timbers will win the conference, making for the most intriguing match of Decision Day. While a draw and a Seattle win would put the Sounders and Whitecaps level on points, Vancouver's higher number of wins ensures they wouldn't slip behind the defending champions.

Chaos out West

Below the Cascadian trio, there's still plenty to play for out West. Sporting Kansas City could sneak into a first-round bye with a win and Seattle and Portland both failing to win their matches. That said, a loss to Real Salt Lake could find SKC falling as far as fifth, failing to secure a crucial home date in the knockout round. This would be a nightmare: Sporting is 15-4-3 at home in postseason play, compared to an appalling 2-16-5 on the road.

While Wilmer Cabrera's revitalized Houston Dynamo side have already punched their ticket, they could overtake Kansas City with a home win over the Chicago Fire and an SKC draw or loss. Meanwhile, only one of San Jose, FC Dallas and RSL will find themselves in postseason play. Seen as a preseason favorite for MLS Cup, Dallas will need the mercurial Minnesota United to come through to keep San Jose from earning a home victory. FCD would then have to finish the job against LA Galaxy. If both of these teams falter, RSL can sneak in with a win over SKC.

Simple, right?

Shoring up the East

While Toronto will likely finish at least 10 points above the second-place team in the East, the next five spots have been as impossible to predict as a kaleidoscope. The second seed in the East is entirely up for grabs. New York City FC will control its own fate; a home win over Columbus Crew SC will separate it from the rest of the pack. Any dropped points will leave things wide open. Chicago and Atlanta United are one and two points behind, respectively. While the Fire face a tough away fixture at Houston, Atlanta will welcome a Toronto side looking to gain sole possession of the record for most points in a season.

Fresh off the bombshell report that owner Anthony Precourt is considering a relocation to Austin, Texas, the Crew will hope to earn a home date by pipping NYCFC at Citi Field. Assuming the fans are still on their side, this would be a massive advantage: Columbus is 12-7-1 at home all time in the playoffs, compared to just 5-14-3 on the road. Meanwhile, the New York Red Bulls are locked into the sixth seed while serving as D.C. United's final opponent at RFK Stadium.

Awards watch

With the regular season coming to a close, MLS awards ballots are due on Monday evening. Diego Valeri became just the second player to ever net 20 goals and 10 assists in a season. He'll face steep competition for MVP, as Chicago's Nemanja Nikolic has all but tied the laces on the Golden Boot after a hat trick last weekend. Meanwhile, NYCFC's David Villa has returned from injury in time to make some noise in the race.

The battle for Rookie of the Year seems to pit two players from expansion sides. Minnesota's Abu Danladi has shown great improvement in the second half of the season, and his eight goals and three assists are a fine return for the top pick in the 2017 SuperDraft. However, the former UCLA striker will need a strong performance to overtake Atlanta's Julian Gressel, who's gone from Neustadt an der Aisch, Germany to the heart of Tata Martino's midfield. In his 23 starts, he has five goals and nine assists.

SKC's Tim Melia seems a safe bet to win Goalkeeper of the Year, helping keep 10 clean sheets for a stout defensive side. Comeback Player of the Year seems far more wide open. Dempsey has led Seattle with 12 goals in league play. Meanwhile, Erick "Cubo" Torres has set a Dynamo record with his 14 goals, and the Crew's Federico Higuain set a career high with 12 assists.