The 2015 MLS playoff field captured the essence of a league often defined by its parity.  The New York Red Bulls and FC Dallas each led their respective conferences with 60 points, seven points more than their closest rivals.  A mere four points separated the remainder of the playoff field.  Now the specter of away goals appears to threaten both of the top seeds – New York and Dallas face long odds to win MLS Cup.

The history of MLS playoffs is a perplexing one.  As an American league, it’s not surprising that MLS would have playoffs at the end of the regular season to crown a champion.  It’s not like playoffs are a friction point between the global nature of soccer and the American nature of MLS; playoffs are prevalent in Latin American leagues (with the exception of Brazil).  However, the myriad formats used over the league’s 20 year history indicate a lack of clarity over two key issues:

  1. How difficult should it be to make the playoffs?
  2. How is regular season performance best rewarded?

MLS playoffs always culminated in a single-game final, but the path to the final has changed every few years.

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The league’s first four years featured a Best of Three format, where the first team to win two games would advance to the next round.  “But wait, don’t some soccer games end in a tie?” you ask.  To which I respond, “Oh, you forgot about 35-yard shootouts.”

For the 2000 season, shootouts joined the great countdown clock in the sky (one of Don Garber’s first initiatives), and MLS embraced draws in the regular season and playoffs.  The Best of Three format morphed into “First to Five”, a three game series in which teams played until one team reached five points.  From an academic perspective, First to Five essentially produced a mini-group stage with home field advantage for the higher seed, but practically, a compressed schedule and poorly attended mid-week games made First to Five less than optimal.

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In 2003, the league sought to simplify the playoff format, and introduced an aggregate home-and-home conference semifinal, a single-game conference final, and MLS Cup.  This general structure remained over the next eight years.  MLS expanded rapidly in the following years, growing from 10 teams in 2003 to 16 in 2010.   With this expansion, MLS demonstrated fluidity in concept of conferences, as playoff brackets included teams from the East or West.

Portland and Vancouver joined the league in 2011, bringing MLS to 18 teams.  MLS expanded the playoff field to 10 teams, and with it the introduction of the knockout round.  Unfortunately, the playoffs became an amalgam of formats, and included a single game knockout round, followed by aggregate semis, followed by a single-game conference final.  Additionally, the top three teams in each conference remained stable, while the other four teams could swap, leading to the confusing placement of New York in the West semis and Colorado in the East semis.

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The next year heralded the single-best playoff addition in MLS history: the team with the better record in MLS Cup would host the final.  However, in the same year, the conference finals became an aggregate match, making the path to the final more difficult for a higher seed.  Perhaps it is a coincidence, but since the change, a #1 seed in either conference has yet to reach the final.

The playoff tinkering was still not complete, and last year, MLS brought away goals to the aggregate legs – a change that remains mystifying.  With the league at 20 teams this year, MLS added an additional two knockout round games, expanding the playoff field to 12 teams.  Sixty percent of the teams qualify for the playoffs, the highest percentage since 2007 (62%).

MLS Playoff Threshold

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Twenty years of shifting playoff formats lend insight into the initial questions of 1) How difficult should it be to make the playoffs?, and 2) How is regular season performance best rewarded? The answer from MLS on the first question is a firm “not very hard”.  2010 was the only year that a majority of the league’s teams did not make the playoffs.  In a league that lacks relegation or a secondary continental tournament (rest in peace, SuperLiga), there’s a desire to maintain interest among the fanbases for mid-table teams.  Unfortunately, the end result is a focus on average teams; for example, in this league announcement, the Supporters’ Shield race garners the fourth bullet point.

The second question of how to reward regular season performance is more nuanced.  Offering more incentives for regular season performance is generally a good thing.  For example, the playoffs are incredibly liberal, but there were strong incentives this season to finish first or second and skip the knockout round.  Additionally, awarding CONCACAF Champions League berths to the conference winners is a good indication that 34 games mean more than five or six to represent MLS internationally.

However, an insistence on aggregate semifinals and conference finals minimizes regular season performance.  To truly align incentives between the regular season and playoffs, why not streamline everything and go single-elimination for the entire playoffs?  MLS home teams tend to win just under half the time,  and splitting the likelihood of a draw brings that win figure up around 60% to 63%.  The figure seems high, but the probabilities of actually winning MLS Cup remain varied.  Assuming a single-round elimination and the home team is always a 60% favorite, the Supporters’ Shield winner would still only have a 22% chance of winning.MLS Playoff Threshold Prob

Now here were the ESPN and Vegas odds at the start of the post-season (with 12 teams)

The chance to win it all isn’t dramatically different by seed, and the playoffs would conclude in three weeks (or four, if MLS retained 12 teams in the playoffs).  The time saved could be used to optimize regular season scheduling, be it alleviating fixture congestion or honoring more international windows.  There is also a clear connection between regular season performance and post-season probability for success, while still including some uncertainty that brings excitement to playoffs.

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