Midfielder Sulley Muntari inspired Serie A leaders Inter Milan to a hard-fought 2-1 win at home to Napoli on Sunday while AC Milan were humbled 3-1 at mid-table Palermo.
Striker Fabrizio Miccoli fired in a superb goal on 50 minutes before Edinson Cavani and Simplicio sealed Palermo's victory with Ronaldinho, who had a spotkick saved at 0-0, netting a late penalty for the shell-shocked visitors.
The champions, who beat Juventus last Saturday thanks to Muntari's goal, went 2-0 up through Ivan Cordoba and the Ghanaian but were forced to hang on after Ezequiel Lavezzi pulled one back on 36 minutes.
Jose Mourinho's side lost 1-0 at home to Panathinaikos in the Champions League in midweek but continue to grind out results in Serie A despite their inconsistency.
Inter have a six-point lead with joint-second AC Milan visiting Palermo in the late game (1930 GMT). Juventus, level with Milan, hammered Reggina 4-0 on Saturday.
"At 1-0 the game seemed over as we were playing so well but you can never say that in football," Mourinho told Sky. "In the second half I don't remember them having a real chance."
Last term's runners-up AS Roma, who had a terrible start, recorded a third straight league win after Francesco Totti netted in the second half to seal a 1-0 victory over Fiorentina.
Adrian Mutu, who almost joined Roma in the close season, went close with a free kick and a header for the visitors but they remain joint fifth with Lazio, who went down 2-0 in soggy Bergamo against midtable Atalanta.
Early season pacesetters Udinese, who had top striker Antonio Di Natale sent off, lost their fourth league game in a row when a late Felipe own goal gave bottom side Chievo a 1-0 away win and ended a six-game losing streak.
At the other end Cordoba settled the San Siro nerves with a superb finish for a defender following Muntari's cross on 16 minutes.
Inter were on top and made fourth-placed Napoli suffer when Muntari turned in Maicon's cross after Julio Cruz's backheel.
The visitors refused to lie down however and were soon back in the hunt when talisman Lavezzi dinked home following another perfect backheel from strike partner Marcelo Zalayeta.
Napoli had much of the play in the second half and the hosts were fortunate when Argentina's Lavezzi was booked for diving in the box in the second half despite replays showing contact between the forward and Maxwell.