Breaking down the best defense in MLS (only 32 goals against, top 5 by xGA) will be a tough task for the Seattle Sounders. Yes, the Colorado Rapids are without Tim Howard, but he is not the reason that their defense has been great. The Rapids use a three-man central midfield - when healthy - of Jermaine Jones, Sam Cronin and Michael Azira. That’s a buzzsaw of strong defensive players.
The backline is huge. Axel Sjoberg, Eric Miller and Marc Burch team up with one of Jared Watts or Bobby Burling. They may not be the most mobile set of defenders in the league, but they defend the air quite well (5th in aerial duals won per game, 4th in % of aerial duals won).