A deadly slip-up by Cagliari defender Diego Lopez paved the way for the Dutchman to slot into an empty net on 65 minutes, when the former collided with keeper Federico Marchetti while trying to head the ball back.

Carlo Ancelotti's side now lie third with 48 points, 11 adrift of leaders Inter Milan.

Cagliari produced a striking display against the Rossoneri, who have several key players on the sidelines due to injuries.

Andriy Shevchenko, Marco Borriello, Ronaldinho and Alexandre Pato, and Kaka are yet to reach recovery.

For this reason, Filippo Inzaghi was deployed as a lone striker, and couldn't make tangible impact upfront.

The Italian veteran had a goal disallowed on 22 minutes after being ruled offside.

David Beckham, who was included in Milan's starting eleven, whipped in some precise crosses at the beginning of the game.

Milan goalie Christian Abbiati kept the score level in the first period after blocking tame efforts by Robert Acquafresca and Andrea Cossu.

After the restart, Cossu came close to scoring, but his unstoppable right-footed strike hit the post.

Milan's fans at the San Siro heaved a sigh of relief when Seedorf broke the deadlock 20 minutes after the interval.