Kevin Forrest, one of numerous backups handed starting assignments by Coach Sigi Schmid, scored in the 62nd minute to decide an evenly played game. Each team took 12 shots, each team took five corner kicks, and each keeper came up with four saves, according to the official statistics.
While the chances of Seattle winning either the MLS Cup or U.S. Open Cup in its first season remain remote, there are memories of the 1998 Chicago Fire, which won both trophies in its inaugural year.
By beating Colorado, Seattle takes the last of eight U.S. Open Cup slots allotted to MLS teams in the third round. A draw will be held next month to determine the pairings in the round of 16 among teams from MLS, USL, PDL and USASA.
Midfielder Freddie Ljungberg, who missed the last two league games because of migraine headaches, had resumed training Monday but was not included in the game-day roster.
Keeper Kasey Keller, defenders Nathan Sturgis and Jhon Kennedy Hurtado, and midfielder Sebastian LeToux retained spots in the starting lineup after playing in a 2-2 tie with Colorado during the weekend in league action. Sturgis, though, played in midfield, where injuries have thinned out Schmid's options, and LeToux played up top with Roger Levesque.
Rapids goalie Preston Burpo fended off two early Seattle opportunities and the teams pressed each other through the first 45 minutes. Rapids coach Gary Smith brought on midfielder Nick LaBrocca for the second half to spark the attack but Seattle dictated most of the play.
Sanna Nyassi tested Burpo early in the second half with a drive the keeper managed to corrall, and Nyassi started the sequence a few minutes later that produced the goal. Levesque flicked the ball into the path of Forrest, and the native of nearby Edmond headed it past Burpo.
Keller pulled off a stunning save in the final minutes on a fierce shot from Michael Holody to end Colorado's last-ditch rally. The Sounders join fellow play-in qualifier D.C. United along with seeded teams Columbus, New England, Houston, Kansas City, Chicago and Chivas USA as the eight MLS representatives.
May 26 in Tukwila, Wash.
Seattle 1, Colorado 0.
Goal:Forrest (Levesque, Nyassi) 62.