The pro-Seattle Sounders crowd arrived excited about a potential third consecutive upset of a Major League Soccer team. Unfortunately for the Sounders...

The pro-Seattle Sounders crowd arrived excited about a potential third consecutive upset of a Major League Soccer team.

Unfortunately for the Sounders, those fans left dejected.

Guatemalan national team member Carlos Ruiz struck in the first minute of overtime and Abe Thompson buried a penalty for a two-goal lead as FC Dallas booted the Sounders 2-1 in overtime in front of an announced crowd of 10,385 fans at Qwest Field in Tuesday night’s semifinals of the 94th Lamar Hunt U.S. Open Cup.

Deep into added time of the 120th minute, Leighton O’Brien of the Sounders knocked in a diving shot off a cross from Andre Schmid to avert the shutout and Seattle (20-8-7 overall) gave one final push in the final minutes of added time.

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It was the Sounders’ first trip to the Open Cup semifinals since 1995 and they missed a shot at their first appearance in the Open Cup finals in franchise history.

Ruiz stunned Seattle in the first minute of overtime for a 1-0 lead, scoring on a short shot at the right post on a nice run after a pass down the right side from Arturo Alvarez. After that, FC Dallas (14-14-5) milked the clock at every turn.

Thompson scored on a penalty kick in the 119th minute for a 2-0 advantage after Zach Scott pulled down Dax McCarty in the penalty area.

“The lesson there is that when you’re playing a team of that caliber, you have to make them pay,” Sounders coach Brian Schmetzer said. “We had chances where we should’ve scored.”

Seattle, now 17-3-4 in its last 24 matches, hoped to become the second non-MLS champion of the Open Cup and first since the Rochester Raging Rhinos in 1999. MLS teams joined the Open Cup in 1996.

The Sounders conclude their ULS First Division regular-season home schedule Thursday against the California Victory and then end the regular season at Minnesota on Sunday.

“This is a challenge for us as pros,” said O’Brien, whose team opens the playoffs Sept. 14-16 and goes for the club’s first league title since 2005. “The Open Cup is kind of a bonus. It would’ve been a great bonus for us to get to the final.”

With the victory, FC Dallas hosts the Open Cup title match against fellow MLS club New England Revolution on Oct. 3 at Pizza Hut Park. The Revolution beat the USL First Division’s Carolina Railhawks 2-1 in overtime in Tuesday’s other semi.

Sounders goalkeeper Chris Eylander punched away a shot attempt from Thompson in the 62nd minute, then survived a 25-yard blast well over the cross bar on the rebound by Alvarez.

The two teams played to a scoreless halftime tie, but the Sounders began to assert themselves offensively late in the first half. Seattle missed a prime scoring chance in the 13th minute when Hugo Alcaraz-Cuellar narrowly flicked a header over the cross bar near the right post after a corner kick from Josh Gardner.