Saborio opened the scoring in the 41st minute when he tapped in Chris Wingert's pass and the goal was allowed to stand after the referee consulted with his assistant as visiting players claimed the Costa Rican was in an offside position.
Salt Lake deserved the lead and would have gone into the break in a more dominant position had it not been for the spectacular goalkeeping of Seattle's Kasey Keller.
However, Saborio would not be denied and struck again in the 53rd minute with a cheeky back-heel and almost bagged a hat-trick 18 minutes later with a shot that flew above the crossbar with Keller beaten.
American Ned Grabavoy sealed the 3-0 victory in the 88th minute, leaving the Sounders facing a monumental task to claw their way back into the tie in the home leg at CenturyLink Field on Wednesday.
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