Readers of this site probably understand why the Seattle Sounders' season-finale against the LA Galaxy is of some importance. If you already are convinced of this, please feel free to skip this. Or, better yet, pass it along to some of your less well-informed friends.
That said, winning this game has everything to do with what it means several weeks and months into the future, rather than anything immediate. In a sense, this game bears little importance to the Sounders' immediate playoff hopes. Whether the Sounders finish No. 2 or 3 in the West really doesn't make any difference in and of itself.
As was illustrated last year, "home-field advantage" in the a two-game aggregate series is basically meaningless. The only way that advantage comes into play is if the series is tied after 180 minutes and there are 30 minutes added on for overtime. That's only happened six times during the 36 previous two-game aggregate playoff series in MLS history, and the home team actually won half of those. The higher seed has gone just 21-15 in the conference semifinals since that format was adopted. In other words, there is no appreciable home-field advantage in a two-game aggregate-goal series.
In that sense, while a tie against the Galaxy would give the Sounders the No. 2 seed, that's at best a
Pyrrhic mostly empty victory.
For this game to really mean something, the Sounders need to win. A win would give the Sounders 59 points and the third highest total in MLS. Why is that important, you ask?
There are two big reasons: CONCACAF Champions League and the MLS Cup.
A third-place overall finish would give the Sounders some room for error in their quest to return to CCL for a fourth straight year. As it stands now, the most straight-forward and only guaranteed way to qualify is for the Sounders to at least advance to the MLS Cup final. With a win against the Galaxy, the Sounders qualify for the 2013-14 CCL if Sporting Kansas City or the San Jose Earthquakes make the MLS Cup final.
Anything less than a win means the Sounders can only qualify by making the MLS Cup. A tie would leave them with 57 points, which is the fourth highest total, but would leave them fifth in the standings and out of the running for a backdoor entry into CCL. With that total, D.C. United would be third and in line to take a CCL berth if either KC or the Earthquakes make it to the final. The New York Red Bulls would be the next team in line if both of those teams made it or if United made the final. Even if the Vancouver Whitecaps were to make the final and not claim the CCL spot that goes with it, both United and the Red Bulls would be in line to claim the unclaimed spots ahead of the Sounders.
Hosting MLS Cup
While homefield advantage may not mean much in a two-game aggregate series, it's quite important in a do-or-die situation. Generally speaking, we say home-field advantage is worth about a goal. In the MLS Cup playoffs where the conference finals have been a one-off game played at the home of the higher seed since 2003, 13 of 18 teams with home-field advantage have won. The home team has also won 12 of the 15 U.S. Open Cup finals played at one team's home stadium during the MLS era, including both times the Sounders hosted it.
A Sounders victory would mean they'd host the MLS Cup final against any team other than Sporting KC, as it would require them to beat the Earthquakes to get there.
Although the Sounders haven't historically been much better at home as they are on the road, this year has been different. The Sounders have claimed 35 points in 17 matches with a +16 goal-difference at CenturyLink. While they have a league-low three road losses and are among the better road teams in MLS, they have still only claimed 21 points and posted a +3 goal-difference in 16 matches.