Four defeats in a row for the Blue and Whites, the latest being at the hands of leaders Barcelona.
Zlatan Ibrahimovic, on for the injured Thierry Henry, opened the scoring for Barcelona and Gerard Pique added a second just after the break.
Real Madrid are keeping up the pressure at the top of La Liga, winning 3-0 against Tenerife although not really getting going until the second half.
Benzema scored the first, nodding in a Xabi Alonso free kick and then seven minutes added a second. Kaka made sure of the three points with a goal in the 77th minute.