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Who will Sounders play in Round of 16?

We did the math and it looks like the most likely opponent is Toronto FC, but it could be one of several others, too.

Courtesy of Major League Soccer

UPDATE: The Vancouver Whitecaps managed to beat the Chicago Fire 2-0, meaning the Sounders secured the No. 2 seed in their group. That means they’ll play the second-place finisher from Group F on Monday at 7 PM. Assuming there’s not a five-goal swing in the standings, that means the Sounders will play the loser of Thursday’s LAFC-Portland Timbers match.

By now, you probably know that the Seattle Sounders’ 3-0 win over the Vancouver Whitecaps qualified them for the MLS is Back Round of 16. Who they will play, however, is a complicated question. After the Sounders took care of the Whitecaps there were at least nine potential opponents. Now it has dropped to six. And while my skills as an MLS analyst are limited, my superpower is the mathematics of playoff tiebreakers, so I thought I would share my insights here.

Prior to Wednesday’s evening matches, there were five games remaining in the group stage, and they all have implications to find the Sounders’ next opponent. When calculating the probabilities of each opponent, I will be leaning on FiveThirtyEight’s Win Probability Model for the basic data and using some guesswork when necessary (like the chances of the LA Galaxy winning by three goals).

Now, let’s get to work.

The first thing we need to know is if the Sounders will finish second or third in their group. If the Chicago Fire can defeat the Whitecaps on Thursday, the Sounders finish third. With any other result, the Sounders finish second because they will have the tiebreaker on Chicago with Goal Differential (GD). Chicago has a 66% chance to win (and obviously a 34% chance of not winning)

If the Sounders finish second in their group, they simply play the No. 2 team in Group F, the so-called Group of Death. Currently, that’s LAFC. But if LAFC can beat Portland (59% chance), then Portland is our opponent. But wait! There is one other crazy option. If LAFC loses and the Houston Dynamo win (only a 7% chance of both happening), Houston could theoretically be our opponent if their winning margin plus LAFC’s losing margin total six goals. The combined probabilities of the stars aligning are significantly less than 1%, so we acknowledge it here, but otherwise ignore it.

LAFC Opponent Odds = 34% * 59% = 20%

Portland Opponent Odds = 34% * 41% = 14%

Now things get tricky. As we said, there is a 66% chance of the Sounders finishing third. If so, they play the winner of either Group C or Group D. But which one? On KJR on Tuesday, Garth Lagerway asked Jackson Felts if he knew and both were not entirely sure. Luckily, MLS finally put out an explanation Tuesday on how this works.

The only part that matters for the Sounders is this: If the top 4 third-place teams come from exactly groups A, B, C, and D than the Sounders would play the winner of Group D. In all other scenarios, the Sounders are destined for another rematch with Toronto FC.

As far as we care, the lowest third-place team in groups A, B, C, and D is NYCFC with 3 points, a GD of -2 and 2 goals scored (GF). It’s true that if Chicago loses, they could be worse, but in that case, we are second in Group B and it’s not our problem. If the third-place team in E or F can beat out NYCFC, we play Toronto.

Let’s start with Group F. If the Dynamo win, then they finish third and pass NYCFC. If the LA Galaxy beat the Dynamo by three goals, then they finish third and pass NYCFC. In all other scenarios (about 60% of the time), NYCFC holds on.

Now for Group E. Third place is the loser of New York Red Bulls and FC Cincinnati. If they tie, then they both advance with 4 points. If the Red Bulls win, then Cincinnati falls behind NYCFC. If Cincinnati wins by two goals or more, then NYRB falls behind NYCFC. If Cincinnati wins by one goal, then NYRB and NYCFC tie for GD and we go to total goals scored. NYCFC wins if NYRB loses 1-0 and NYRB passes NYCFC if they manage to lose 3-2 or 4-3, etc.

What happens if NYRB lose to FC Cincinnati by a perfectly reasonable score of 2-1 you ask? Well, it comes down to fewest disciplinary points, where a foul is 1 point, a yellow card is 3 points and a red card is 7 points. NYCFC has accumulated 63 points over 3 games, while NYRB has 39 points over 2 games. Overall, I have NYCFC staying ahead of the Group E team at 68%.

When we pop all the combinations above into the calculator, a little guesswork, carry the one, and we get about a 59% that a third-place Sounders team plays Toronto and 41% of the time that a third-place Sounders team places the winner of Group D.

Toronto Opponent Odds = 66% * 59% = 39%

Finally, determining the winner of group D is pretty simple. If Minnesota United FC wins tonight (54% chance), then they win group D. Otherwise, Sporting KC wins the group.

Minnesota Opponent Odds = 66% * 41% * 54% = 15%

Sporting KC Opponent Odds = 66% * 41% * 46% = 12%

That’s all there is to it.

So, in Summary:

39% Toronto – Requires:

  • LAG L OR LAG W by 3 goals OR NYRB-CIN Tie OR NYRB lose 3-2, 4-3, etc. (or possibly lose 2-1)

20% Portland – Requires:

  • CHI L or Tie
  • LAFC W

15% Minnesota – Requires:

  • LAG Tie or LAG W by 1-2 Goals AND
  • NYRB W OR NYRB L by 2 Goals OR NYRB score 0 goals (or possibly lose 2-1)
  • MIN W

14% LAFC – Requires:

  • CHI L or Tie AND
  • LAFC L or Tie

12% Sporting KC – Requires:

  • LAG Tie or LAG W by 1-2 Goals AND
  • NYRB W OR NYRB L by 2 Goals OR NYRB score 0 goals (or possibly lose 2-1)
  • MIN L or Tie

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