The Portland Timbers comprehensively inflicted only the third defeat of the season on the Los Angeles Galaxy as they ran out 3-0 winners on Wednesday.
Quickfire strikes from Mike Chabala and Jorge Perlaza midway through the first half had them on top and Eric Brunner capped it in the 68th minute.
In the East, the Philadelphia Union failed to move level with the Columbus Crew as they were held to a 1-1 draw by the Fire in Chicago. Philadelphia led through Veljko Paunovic's 34th minute goal, but Pavel Pardo levelled nine minutes into the second half.
Sporting Kansas City played most of the second half with 10 men but nevertheless completed a relatively comfortable 2-0 win over Real Salt Lake. The hosts had taken the lead with two goals in the space of five first-half minutes from Roger Espinoza and Teal Bunbury, and were not unduly troubled even after the 57th minute dismissal of Espinoza.