MARCELO Zalayeta struck 17 minutes from time to earn Napoli a shock 1-0 win over Inter Milan, their first under Roberto Donadoni.
Inter boss Jose Mourinho saw his side's lead over AC Milan cut to seven points with five games remaining after their earlier victory over Palermo at the San Siro.
Ezequel Lavezzi laid on the winner beating two Inter defenders before setting up Zalayeta who beat Julio Cesar with a shot from the edge of the penalty area.
Earlier AC Milan had beaten 10-man Palermo 3-0 to move two points clear of third-placed Juventus.
A penalty from Kaka and a header from Filippo Inzaghi ensured Milan were already firmly in control before Cesare Bovo received his marching orders three minutes into the second half.
Kaka, who seemed back to his best after an injury-plagued few months, slotted home another penalty eight minutes later to seal the victory.
Juventus twice came from behind to deny Reggina a much-needed win in their fight against the drop with a 2-2 draw.
Jose Leonardo Talamonti ended Atalanta's run of four games without a win with the only goal of the game away to former club Lazio.
Bologna defeated Genoa 2-0, Sampdoria drew 3-3 with Cagliari, Torino defeated Siena 1-0 and Lecce beat Catania 2-1