PORTLAND, Ore. (AP) — The Portland Timbers did what they needed to do at home for the first go-round against the rival Seattle Sounders in the MLS playoffs.

Sebastian Blanco put the Timbers in front with a goal in the 29th minute and Portland hung on over a tense second half to go up 2-1 in the opening leg of their Western Conference semifinal against the Sounders on Sunday.

The second leg is set for Thursday night in Seattle.

“We won, that’s the important thing,” Timbers coach Giovanni Savarese said. “We’ll think about everything else later. We needed a win today and found the win that we needed.”

Seattle was hurt by a pair of key injuries to starters Cristian Roldan and Chad Marshall in the opening half that could impact the second leg.

“Obviously it wasn’t the result that we wanted, but at the end of the day we got a road goal, so that always helps. It’s something to put in your pocket for later. But we understand win the game on Thursday. Those are the facts,” Sounders coach Brian Schmetzer said.

Seattle, the second seed in the West, had avoided a knockout round game this week after wrapping up the regular season with a 2-1 victory over the San Jose Earthquakes. The win, secured on Raul Ruidiaz’s stoppage-time goal, combined with Colorado’s Decision Day victory over FC Dallas, slid the Sounders into second place in the standings for the opening round bye.

The Sounders won 14 of their final 16 regular-season games in another remarkable second-half surge under Schmetzer.

Fifth-seeded Portland lost its final regular-season match against the Whitecaps and had the daunting task of facing FC Dallas on the road in the knockout stage. But the Timbers pulled off a 2-1 upset with a pair of goals from Diego Valeri, despite playing for much of the second half a man down.

The victory set up the Cascadia semifinal between the two teams, who last met in the 2013 conference finals with Portland winning 5-3 on aggregate.

Ruidiaz scored in the 10th minute to give the Sounders the early lead. Roldan moved the ball up the left side and passed it off to Victor Rodriguez, who served it into Ruidiaz out in front of the goal. Ruidiaz tucked his shot into the left side of the net out of Jeff Attinella’s reach. It was his 11th goal this season.

The Sounders went into the match 12-0-0 in MLS playoff games when they scored first.

But the Timbers pulled even a short time later on Jeremy Ebobisse’s goal. Stefan Frei rushed Ebobisse and slid to try to stop the ball, but Ebobisse got it past him and the shot sailed into the net in the 16th minutes

Blanco maneuvered around several defenders before a clinical finish out of Frei’s reach to put Portland in front.

“We won. This is important. Now we need to rest and play the next game in Seattle,” Blanco said. “Very hard.”

Roldan had to leave the game in the 31st Minute with a groin injury. He was replaced by Waylon Francis. Seattle also lost midfielder Marshall, who had to be stretchered off the field with a right knee injury. He was replaced by Roman Torres in the 40th minute.

Schmetzer said the two would be evaluated once the team returned to Seattle.

The Timbers thought they had another goal in the 80th minute on Lucas Melano’s rebound but it was called offside.

“I think when we went out in the second half we controlled the game,” said Sounders defender Kelvin Leerdam. “Of course they got some chances, but I’m very positive with what we’ve show in the second half and I believe we can take that to our home game, and I believe we can finish it out”

The two teams met three times during the regular season, but Seattle won the last one 1-0 at Providence Park.

Portland was without Larrys Mabiala after he was sent off with a red card in the match against Dallas.