HOUSTON (AP) — Jeff Attinella had two saves to help the Portland Timbers to a 0-0 draw with the Houston Dynamo on Monday night in the opener of their Western Conference semifinal.

The second leg of the two-game aggregate series is Sunday in Portland. The fourth-seeded Dynamo had just one road win in the regular season.

Attinella posted his 10th career shutout in his first playoff action — including a sliding 1-on-1 save against Alberth Elis in the 51st minute and a leaping stop of a header by Philippe Senderos in the 56th.

Houston is unbeaten in its last eight matches, including a 1-0 win over Sporting Kansas City in Thursday's single-elimination knockout round.

The Dynamo were awarded a penalty kick in the 30th minute after Larryss Mabiala's sliding tackle of Alberth Elis at the corner of the 6-yard box, but the call was overturned after a replay review.

Mabiala, a defender, as well as midfielders Darlington Nagbe and Diego Chara — who was taken off on a stretcher — did not return for Portland after injuries midway through the game.

The top-seeded Timbers were already without Fanendo Adi, Sebastian Blanco and David Guzman. Adi was second on the team with 10 goals despite missing the final 10 regular-season games after he injured a hamstring during a 3-1 win over Los Angeles on Aug. 6.