Vancouver blocked the first two shot attempts of the sequence, and then Nyassi smashed the left-footed strike from near the penalty spot into the left corner of the goal. It was his first career goal with the Earthquakes (3-3-0).
David Bingham earned his first career shutout without a save while the Quakes snapped an eight-game winless streak against the Whitecaps (4-2-1).
Vancouver was playing its second game of the week after a 2-2 draw with the Columbus Crew on Wednesday night.
Pedro Morales and Adam Jahn both received red cards in the 88th minute for a brief altercation. Jahn went down, and Morales kicked at the ball near Jahn's midsection after the whistle. Jahn kicked back at Morales' shins in retaliation.