HOUSTON (AP) -- The Houston Dynamo played out a scoreless draw with Deportivo Saprissa of Costa Rica in the first leg of their CONCACAF Champions' Cup semifinal Wednesday.

Pat Onstad made seven saves for the Dynamo, which took 17 shots to Saprissa's eight. Two headers by Brian Ching went high, and several chances by Franco Caraccio were thwarted by Saprissa goalkeeper Keilor Navas, who had four saves.

Andres Nunez led Saprissa with three shots on goal, all of them coming in the first half.

Saprissa's final chance came in the last moments of the game as Michael Barrantes dribbled down the field and let one fly from the upper box that Onstad batted down.

Houston reached the CONCACAF Champions' Cup semis last year where they lost to Pachuca from Mexico.

The second leg of the series is next Wednesday in Costa Rica.

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