Osvaldo Alonso scored a huge away goal for Seattle as the Sounders came from behind to earn a 1-1 draw at Toyota Park in Dallas.
The teams face off again in Seattle on November 10th as FC Dallas will have to earn a result to advance to the conference finals.
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Seattle looked like they were going to take the lead as Obafemi Martins found himself one-on-one with the goalkeeper in the 18th minute. However, the Nigerian international was stopped by Raul Fernandez as Toyota Park breathed a collective sigh of relief.
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Neither team looked very dangerous in the first half but FC Dallas got on the board first as Michel scored from the penalty spot for the second straight game.
Andres Escobar cut towards the end line as he was taken out by a needless challenge from Marco Pappa. Referee Allen Chapman had no choice but to point to the spot, and Pappa was punished for his clumsy defense as Michel converted to give Dallas a 1-0 lead.
Seattle nearly equalized at the brink of halftime as it was Martins again beating his defender and firing a shot on net, where Raul Fernandez made a huge save for Dallas. Clint Dempsey was keen to tap in the rebound only to see the ball cleared off the line by Dallas defender Matt Hedges.
The Sounders finally got a crucial away goal in the 54th minute asa Osvaldo Alonso headed home a Marco Pappa free-kick. It was poor defending from Dallas as Osvaldo went unmarked and was left with an open header on net.
Dallas: Fernandez, Hernandez, Loyd, Hedges, Watson, Castillo, Akindele, Ulloa, Michel, Escobar (Texeira 86′), Perez
Goal: Michel (34′ PK)
Seattle: Frei, Gonzalez, Marshall, Yedlin, Scott, Evans, Alonso, Pappa (Azira 72′), Neagle (Cooper 65′), Dempsey, Martins
Goal: Alonso (54′)