Peter Nowak started the two Farfan brothers, Gabriel and Michael, in place of Califf and Harvey. The two newcomers were joined by veterans Carlos Valdes and Sheanon Williams, and all four held their composure as Portland surged early in the first half.
Buoyed by the electric atmosphere created by the Timbers Army, Portland forwards Kenny Cooper and Jorge Perlaza made a number of sharp runs into the Union's 18-yard box in the first half-hour. But they couldn't produce any quality chances, and goalkeeper Faryd Mondragon cleaned up any loose balls that came his way.
The Union (4-2-1, 13 points) finally got a few chances late in the first half. The best came in the 43d minute, when Danny Mwanga broke free on the right side and played a cross that was intercepted and redirected to Sebastien Le Toux in the middle of the 18-yard box. But with a defender draped on his back, Le Toux could only shoot the ball into goalkeeper Troy Perkins' path.
The first half ended scoreless, with the Timbers (4-3-1, 13 points) holding a 5-1 advantage in shots on goal.
As the second half unfolded, Union coach Peter Nowak opened up his team's attack, starting with the substitution of Kyle Nakazawa for Gabriel Farfan in the 65th minute.
In the 70th minute, former Portland resident Danny Mwanga set up a great chance by dribbling past multiple Timbers defenders and laying a pass for Justin Mapp on the right flank. Mapp's cross found Carlos Ruiz's head, but Ruiz could not get the shot on target.
In the 72d minute, the Union's resistance was finally broken. Jack Jewsbury took a free kick from midway into the Union's half of the field, and Danso headed the ball past a helpless Faryd Mondragon.
Nowak used his remaining substitutes in the 78th minute, bringing in Jack McInerney for Amobi Okugo and Roger Torres for Justin Mapp.
Le Toux had the Union's best chance to grab a late equalizer, in the 87th minute. A flick into the box by Mwanga went to Williams, whose shot was redirected to Le Toux. The French forward had a chance to shoot, but he fired straight at Perkins from close range.