In a sense, the math that puts the Seattle Sounders through to the Western Conference finals is very straightforward. If they win, no matter the score, they go on. If they don’t? Then the Sounders’ only hope of advancement is for tonight’s match against the Vancouver Whitecaps to end 0-0 in regulation — or tied by any score in added time — and to win the penalty shootout. Any loss or a tie that results in each team scoring at least once put the Whitecaps through.
But if the question is “how good of a chance do the Sounders have to advance?”, that’s a bit more complicated.
FiveThirtyEight, the website best known for prognosticating possible outcomes of elections, has a tool called SPI that they use to predict sporting outcomes. It gives the Sounders a solid 67 percent chance of advancing and 38 percent odds of making it all the way to the MLS Cup final.
Looked at another way, the Sounders earned themselves a result good enough to advance in 71 percent of their home games this year, and 76 percent of their results would have at least earned them added time. Among those results was the lone time they hosted the Whitecaps, a 3-0 win that happened a little more than a month ago.
The Whitecaps, though, were one of the best road teams in the league this year, claiming 20 points. Nearly half of their road results (47 percent) would have been good enough to put them through if they repeated them tonight.
It’s probably worth noting that the Whitecaps were in a similar position the last time they made the playoffs. Back in 2015, they were the higher seed and took a 0-0 tie back to Vancouver for the second leg. The Portland Timbers won that match 2-0. The Sounders, too, know first-hand that’s it’s possible to take a 0-0 tie on the road and come out victorious, after beating RSL 1-0 in that scenario back in 2012. In fact, in the entire history of MLS two-legged playoffs, higher seeds have only a slight 5-4 series advantage when tying the first leg 0-0 on the road.
But history can only tell us so much. The Sounders know what they have to do. Now they need to do it.