By Harrison Crow (@harrison_crow)
Let’s talk nerdy for a second and look at the atrocious and visually unappealing Seattle-Vancouver 0-0 tie from the standpoint of game theory and probabilities.
On the broadcast, Sounders head coach Brian Schmetzer stressed during the pregame interview the importance of his team earning a clean sheet. That telegraphed to both viewers at home and his opponents' that he planned to take a defensive first approach on the road. Hardly a surprising move.
Likewise, Carl Robinson, the Vancouver Whitecaps head coach, made it clear through social media leading up to the match that he would be utilizing his depth given health issues for Jordy Reyna and Cristian Techera, limiting an attack that ranked 15th in total expected goals.
As we know, the rivals ultimately managed what we assume was the zero-zero draw both desired from the outset. The result on social media has been presented in different ways to have mutually benefited each side in different ways. But did it really?
Robinson suggested after the match that "In two-legged ties, conceding at home is a no-no. I learned that years ago. That was the mindset.” The argument springing from the quote is simple: with Vancouver managing to secure the series tiebreaker and having prevented Seattle from scoring, all Vancouver needs now is to score and a draw in the 2nd leg to win the series. Effectually this has forced the Sounders into a must win scenario.
Still, Seattle remains the probable winner in the series with a strong 65% probability of winning the match tonight (according to 538). Still, the idea that Vancouver benefited most from a zero-zero draw actually holds a bit of water.
Before last week’s game, 538’s prediction model gave Vancouver about a 25% probability of winning the series, with Seattle earning just less than 50% and the other quarter tied up in one of the teams advancing on away-goals or penalties.
Earning a draw last week where both teams scored would have dropped the Whitecaps probability to advance to 15%, but since they prevented Seattle from scoring an away-goal, the draw was actually a net positive for the Whitecaps, landing them at a 38% chance at marching on to the next round.
Being that Vancouver was without their best attacking pieces, the team was perhaps in best position to lean upon defensive tactics and simply shoot for a net gain of added probability.
Had Vancouver managed to score and instead got a 1-1 draw or, a 2-2 or 3-3 draw, due to overextending the attack or just being less compact and giving Nicolas Lodeiro room to roam, the benefit would have been far less. In fact, if the first leg had ended in a tie with multiple goals, Seattle would have likely improved their odds of advancing.
Over this past season the average number of goals a winning team needed during a regular season match scored was almost three. The average number of goals per team in over 96 MLS draws this season was just over one. Had the Whitecaps allowed a goal the added probability of them winning this series would have shrunk to less than 20% and a second goal allowed would have nearly eliminated them. By not only drawing the game but preventing the Sounders from scoring, the Whitecaps boosted their chances.
Likewise the Sounders, despite adding 14% probability from earning a draw, improved their odds less than if they had extended themselves and earned a road goal. The conservative approach of Schmezter not only limited Lodeiro (see: Expected Goal Chains and Expected Build-up) but limited the team to the least positive outcome available (i.e. they’re in essentially the same place that they were before the 1st leg started).
Because only one result (another 0-0 tie after 90 minutes) will send the series to extra time, that original 25% chance the winner will be decided on tiebreakers or in extra time saw the greatest drop in likelihood. In other words, both Vancouver AND Seattle saw their odds to advance after 180 minutes increase.
While the Sounders added more net probability for advancing (by 1%) than their opponents, they had less to lose by extending themselves and playing the attacking style of soccer that during the season had them atop the expected goal difference charts.
The Sounders are a formidable team and with the injuries and suspensions there is a certain appreciation, much as in Vancouver’s case, to grab what they could without losing anything in return. But they left more probability on the table as a result of their tactics in the first leg.
Should the Rave Green be unable to pass by the Whitecaps tonight, Sunday will be a certain case of second guessing. But why wait?