A header by Brad Evans in the 78th minute gave Seattle a 3-2 win over CD Marathon, which had come from behind twice on penalty kicks.
When the home side couldn't equalize a third time, the Sounders moved to 3-0 in CCL Group 4. That clinched their spot at the top of the group regardless of what happens in the Oct. 24 rematch, when Marathon (0-1-1) visits CenturyLink Field. As a result, the Sounders are the first club assured of advancing to the CCL quarterfinal round when the tournament resumes in spring.
Seattle jumped ahead in the 11th minute, when Sammy Ochoa headed home a cross from Mario Martinez, who was playing in his hometown.
Marathon equalized in the 35th minute, when goalkeeper Michael Gspurning was called for a penalty in the box, and then couldn't quite deflect away Luis Berrios' PK.
The Sounders slipped ahead again in the 62nd minute when Eddie Johnson scored from inside the area after taking a pass from Andy Rose.
Berrios pulled Marathon even again in the 68th minute on another penalty kick, this time after Patrick Ianni and Julian Rapalo tumbled together in the area.
What proved to be the game-winner combined a couple of players who had subbed on in the second half: Osvaldo Alonso, who came on in the 61st minute, assisting Evans, who came on in the 69th.
The Sounders return to Major League Soccer action at 7:30 p.m. Saturday, playing host to league-leading San Jose. The Earthquakes moved nine points ahead of Seattle on Wednesday, coming from two goals down to earn a 2-2 draw with Portland.
It was partly with an eye to the Quakes' visit that coach Sigi Schmid had kept Fredy Montero, Alonso and Evans out of the starting lineup, and had left players such as Mauro Rosales and Christian Tiffert back home in Seattle.
"(Clinching) the group, that's something we want to do, but we also want to keep our eye on the game on Saturday and make sure we're ready for that one, as well," Schmid said before the team flew to Honduras. "...I think Rosales could probably (have played) if we needed to. Tiffert could probably (have played) if we needed to; but we're going to hold them a little bit for Saturday."
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