The American international struck a crucial second-half goal that put his team on the brink of the CCL final
The result leaves the MLS side with a massive task ahead of next week's second leg in Torreón.
Both teams struggled through the first half, which featured a number of turnovers. Gomez and Darwin Quintero had half-chances, but stand-in goalkeeper Marcus Hahnemann was rarely troubled.
The home side was missing the potent duo of Obafemi Martins and Eddie Johnson and it showed, as the Sounders struggled to generate offense. Osvaldo Alonso had the best chance of the half right before the break, but couldn't connect on a half volley right in front of goal.
Santos got a massive away goal 10 minutes into the second half. Quintero struck a fierce effort from the top of the box which Hahnemann could only parry into the ground. Gomez was on hand to deliver a stinging first-time follow-up which gave the Sounders goalkeeper no chance.
The home side huffed and puffed but rarely troubled Santos keeper Oswaldo Sanchez, despite holding an 11-1 corner kick advantage. In truth, it was the away side which looked more likely to add a second, but the goal never came. Unless Seattle conjures a flawless second leg performance, it likely won't be needed.
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