Gershon Koffie was then guilty of squandering a couple of chances for the Whitecaps, as Portland finally managed an attack of their own, but Rodney Wallace couldn't find the target after being played clean through.
The home side did take the lead midway through the half when Sanvezzo curled in one of his trademark free kicks from just outside the box.
Wallace and Will Johnson both had close-range efforts blocked as the half drew to a close.
The Timbers did get an equaliser shortly after the break, when after seeing his shot strike Andy O'Brien on the hand inside the box, Johnson stepped up to slot his penalty into the bottom left corner.
Their lead did not last long, though, as two minutes later Sanvezzo found Koffie in space just outside the box, and after the bringing the ball under control, the midfielder smashed it into the top corner.
Johnson and Wallace both missed further chances as the Timbers pushed for a second equaliser, but with five minutes to go, a rash challenge from Danso saw them reduced to 10 men.
That didn't stop them drawing level for a second time, though, as Valencia smashed the ball in from close range following a corner.
Despite a late onslaught from Vancouver, they were unable to take the lead for a third time.