Nathan Fogaca, a 22-year-old making his MLS debut, tallied twice for the Timbers (3-3-6, 15 points), who improved to 4-0-2 in their past six matches against Kansas City. Bill Tuiloma, Marvin Loria and Santiago Moreno also scored for Portland, which broke a franchise record for most goals in a game.
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The Timbers took the lead in the 12th minute.
Eryk Williamson took a free kick from about 30 yards out on the right wing and found Tuiloma at the top of the 6-yard box. His forceful header beat diving Kansas City goalkeeper Tim Melia and took one bounce off the turf before crossing the goal line.
Blanco took over early in the second half.
He made it 2-0 in the 46th minute, taking a looping pass from Cristhian Paredes and putting a volley from about 12 yards out on the left side of the penalty area past Melia.
Blanco scored again in the 52nd minute. He took a pass from Yimmi Chara at midfield and drove to the top left of the penalty area before cutting back toward the middle and putting a right-footed shot into the far side netting from 15 yards.
Blanco's lead pass into the penalty area set up Fogaca's first in the 56th minute, making it 4-0.
Russell got Kansas City on the board a minute later on a tap-in at the right post.
Blanco had a chance for the first hat trick in Timbers history in the 69th minute, but instead crossed the ball to Fogaca for his second.
Tzionis scored on a header off a free kick in the 75th minute to make it 5-2.
But Loria tallied on a 12-yard blast in the 88th minute and Moreno capped the scoring on a breakaway in second-half stoppage time.
Both teams finished with 10 men as Portland's Josecarlos Van Rankin and Kansas City's Robert Voloder received their second yellow cards in the 74th and 78th minutes, respectively.