FRISCO, Texas -- Emergency starter Zach Wells made three saves to help the Houston Dynamo tie FC Dallas 0-0 on Saturday.

Pat Onstad, the MLS leader in goals-against average, twisted his back during warmups. Onstad was to be further evaluated when the team returned to Houston.

Wells made leaping two-handed saves on shots by Dominic Oduro and Carlos Ruiz in the 14th and 15th minutes. Houston (7-5-2) has now gone 335 minutes without surrendering a goal and is 5-0-1 in its last six games.

Dynamo midfielder Dwayne DeRosario almost scored in the 85th minute when he fired an open shot from about 15 yards away, but Dallas goalkeeper Dario Sala came out of the box to deflect the attempt. Sala also finished the game with three saves.

FC Dallas (8-6-2) played the game without starting defenders Alex Yi (left hamstring), Chris Gbandi (suspension) and Drew Moor (international duty) but still held Houston without a shot on goal until the 38th minute on a free kick by Brad Davis. For the game, the Hoops outshot Houston 14-8.

Dynamo defender Eddie Robinson will miss the team's next game on July 5 against New York with a one-game suspension after he received up his sixth yellow card of the season in the 29th minute for a reckless foul.