A second-half goal by Luca Saudati gave Tuscan minnows Empoli a 1-0 win at AC Milan on Sunday as the European champions continued their wretched home form.
Milan are still looking for their first league win at the San Siro this season and after eight games they are 11th with 10 points, half as many as leaders Inter Milan, who beat Reggina 1-0 on Saturday.
Juventus climbed to second with 17 points thanks to a 1-0 win over Genoa in Turin in the late Sunday game.
Captain Alessandro Del Piero, who extended his contract with Juve to 2010 this week, decided the match in the 36th minute when he tucked away a whipped-in cross from Pavel Nedved.
Nedved, who was earlier booked for a rash challenge, was shown the red card after the final whistle for dissent.
At the San Siro Milan striker Filippo Inzaghi wasted a pair of good chances in the first half, while Davide Moro and Antonio Busce came close for Empoli.
Saudati headed wide with the net at his mercy just after the break, but he made no mistake with a Francesco Marianini cross in the 55th minute.
The visitors had to play the closing stages with ten men after defender Richard Vanigli came off injured with all the substitutions used, but they still managed to hang on.
"The championship is still long, but we have not done well enough at home. Three points from four games is a negative record," Milan coach Carlo Ancelotti told Sky television.
"When the spaces are tight we lack the movement needed to create chances. We play far too slowly and don't put much pressure [on our opponents]."
Captain Paolo Maldini made his first appearance for Milan since May's Champions League final after recovering from knee surgery.
Before kickoff Brazilian goalkeeper Dida did a tour of the stadium bowing to fans, apparently to apologise for the incident at Celtic that cost him a two-match Champions League ban.
Unbeaten Fiorentina are third with 16 points after defeating Tuscan rivals Siena 3-0.
The Florence side took the lead in the 15th minute when Giampaolo Pazzini controlled a Franco Semioli header and scissor-kicked the ball home.
Adrian Mutu fired in a clever back-heeled pass from Pazzini to double the advantage in the 31st minute. Christian Vieri put the outcome beyond doubt in the 71st minute.
AS Roma, who were held to a thrilling 4-4 draw by Napoli on Saturday, are fourth with 15 points.
