The Portland Timbers their face arch-rival Seattle Sounders in a matchup of teams with Supporters' Shield aspirations.
A victory would not only propel the Timbers past Seattle and Real Salt Lake into first place in the MLS Western Conference with two matches to go in the regular season, it would also send the Sounders on a three-match losing skid that could see them tumble even further down the West standings as the playoffs draw closer.
The Sounders are in freefall after suffering a pair of blowout losses that have raised major questions about their defense, and team's overall form in the final month of the regular season. Seattle has allowed nine goals in its past two matches, which could set up Portland's attack for a field day, with Diego Valeri and Darlington Nagbe ready to take advantage of the Sounders' defensive frailties.
The Timbers will be missing Rodney Wallace, who is on international duty with Costa Rica, but newly acquired Maximiliano Urruti will look to continue his impressive run as the lead forward in Portland's attack, and could cause Seattle's center backs problems with his movement.
Perhaps tougher for Seattle than stopping Portland will be trying to score on a Timbers attack that has posted three straight home shutouts at Jeld-Wen Field, where the Timbers are unbeaten in 13 straight matches (and recorded nine shutouts during that span).
Scoring won't come easy for a Seattle attack that will be without star striker Eddie Johnson, who suffered a groin injury while on U.S. national team duty. Clint Dempsey is still recovering from his own injury issues, and may not be ready to start either. The Sounders will look to rely on Obafemi Martins and Lamar Neagle to lead their attack, with Mauro Rosales trying to pull the strings while battling with the Portland central midfield tandem of Will Johnson and Diego Chara.
Portland and Seattle are in the midst of the Supporters' Shield race, with Sunday's winner moving into pole position in the race. If the Sounders and Timbers tie, the New York Red Bulls will maintain their hold on the top spot in the race with two matches remaining.
The Timbers-Sounders match also has implications in the Cascadia Cup, the competition between Portland, Seattle and Vancouver. A Sounders win would give them the trophy for 2013, while a Portland win or draw would make Vancouver this year's Cascadia Cup winner.