The Timbers dealt the Whitecaps the double blow of a 3-0 scoreline and the seizure of their playoff spot.
While Vancouver is only a point behind with a game in hand, the victory is a huge mental boost for Portland, which looked to be out of the playoff race earlier this season. But with four wins in their last seven MLS games, Caleb Porter's team has charged back into contention.
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The teams endured a scoreless first half before the Timbers offense sprang to life in the second period. Alvas Powell headed home a Diego Valeri cross at the near post in the 51st minute to get the visitors on the board and Maximiliano Urruti and Rodney Wallace found the net in the 75th and 79th minutes to finish the job.
And now, despite a start of eight games without a win and the West's worst defensive record, the 8-8-10 Timbers are in the playoff hunt as the season hurtles down the home stretch.
Portland and Vancouver will meet once more this season, in a potentially crucial match at Providence Park on Sept. 20.