For the past few weeks, we have been including each team's probabilities of earning a playoff spot and each team's probabilities of winning the Supporters' Shield (for most points in MLS). Due to the complexity of the tie-breaker system, I have avoided that topic altogether. Until now. Now that every team with at least 7 caring fans has just one match remaining---Chivas USA has two---I have recalculated the actual playoff chances below using our model, accounting for the various tie-breakers. Let's get started easy. The five Western Conference playoff teams may not be mathematically determined; however, by probability, the top five teams today are certain to remain the same. San Jose could tie Seattle and/or Colorado for the fifth-and-final spot, but the first tie-breaker is total wins, and Seattle has that one covered. The second tie-breaker (which would go into effect only against Colorado) is goals scored. Right now San Jose trails Colorado by 12 goals, meaning that San Jose would have to score at least 13 goals to win all the relevant tie-breakers. So yes, the top five in the West can safely be etched in stone.
Seeds are still important, though. Earning a top-three finish allows a team to avoid that one-game playoff between the fourth and fifth-ranked teams in each conference. Below I have given some relevant probabilities for each team's seeding:
The Portland Timbers could theoretically finish anywhere from first to fourth, though with their final game against Chivas, first place is the most likely. Our model gives Portland a 52-percent chance to beat Chivas on the road and lock up the top spot regardless of other outcomes. However, a tie or loss to Chivas leaves the door wide open for the other playoff teams, and thus Portland's overall chances at first place increase only marginally to about 54 percent. Its chances of a dreaded fourth-place finish require a string of results that has just a four-percent likelihood.
Real Salt Lake guarantees itself at least second place in the West with a win. It has about a 42-percent shot at first place, and only a one-percent shot at fourth place---a result that would require a loss to Chivas at home, a Colorado win at Vancouver, and a tie between Los Angeles and Seattle. Thus both RSL and Portland are not likely to find themselves playing in a one-game playoff, and even in that worst-case scenario, either team would get to play at home.
Probabilities surround the LA Galaxy are a little trickier. Finishing in first place would require a win against the Sounders in addition to Chivas getting points in consecutive matches against RSL and the Timbers. That probability is only about three percent. There is, however, a very real chance that the Galaxy finish in fourth or fifth. A loss to Seattle coupled with a Colorado win leaves them in fifth, while a tie in Seattle and a Colorado win would drop LA to fourth. Those probabilities are 11 and 10 percent, respectively. Thus the remaining 76 percent has the Galaxy finishing in either third or second place.
Seattle's football club could finish anywhere between first and fifth. The unlikely sequence that would vault the Sounders into first place includes them beating the Galaxy, Chivas getting points at RSL on Wednesday, and then Chivas returning home to beat Portland at home on Saturday...but that has just a one-percent likelihood. A loss or tie against the Galaxy locks Seattle into the play-in game. Though playing at home, our model really likes LA and gives the Sounders just a 30-percent chance of winning that matchup. That leaves them with a 32-percent chance at fourth and a 38-percent chance at fifth place.
Colorado is in a rough spot, as it would lose potential tie-breakers to Seattle, LA and RSL. Taking first place would require that Colorado win at Vancouver, that Portland and RSL both lose to Chivas, and that Seattle and LA tie. That string of events has virtually a zero-percent chance of happening. Colorado is much more likely to find itself in fifth place. A loss would guarantee the Rapids the last playoff spot, and a tie would stick them there, too, so long as Seattle earned at least a point against LA. All that adds up to a 51-percent chance at finishing fifth and having to play a one-game playoff on the road.
Here's the chart that sums up all of the probabilities for each playoff contender: