Meanwhile, the Union were trying to become the third MLS expansion team to open its season with a victory.
The physical tone of the first half was set early when Union defender Danny Califf received a yellow card for unsporting behavior in the first minute.
It was one of three cautions in the first half for the Union. They had five yellow cards in the game.
"Defensively, we were too light and were letting guys run by us," Califf said.
The Union had the first good scoring chance when midfielder Michael Orosco sent a blast that 40-year-old goalie Kasey Keller tipped over the crossbar in the sixth minute.
Seattle scored the first goal of the MLS season in the 12th minute when dangerous Fredy Montero fed Steve Zakuani, who found an unmarked Brad Evans eight yards from the goal. Evans one-timed it past goalkeeper Chris Seitz, and the sellout crowd of 36,241 mostly green-clad fans exploded.
It would not be the last time that the Union would hear from Montero, a 22-year-old Colombian who scored 12 goals last season.
Seattle kept applying the pressure until Union forward Sebastien Le Toux, a Sounder himself last season, broke free from a defender, spun around, and shot at an angle right at Keller in the 18th minute.
Union defender Toni Stahl, not using a lot of finesse, received a yellow card for unsporting behavior in the 23d minute. It would be a sign of worse things to come for the Union.
Montero kept applying the heat on the Union, shooting wide on a blast in the 27th minute and a few minutes later kicking it right at Seitz from about nine yards out.
The game turned for the worse for the Union in the 41st minute when Stahl received his second yellow card and subsequent red card for a reckless foul on Montero. Stahl had leveled the Sounders forward.
