Kyle Beckerman put a pass into the penalty area in the 60th minute and Saborío jumped to meet it, redirecting the ball into the corner of the net to break a scoreless tie.
The Costa Rican struck again just 2 minutes later, scoring off a cross from Chris Wingert.
Saborio's header in the 75th minute capped the scoring for Salt Lake (11-6-3), which ended a four-game winless streak and remained in second place in the Western Conference.
Portland (5-8-4) fell to 0-6-2 on the road.
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