Juventus maintained their three-point lead at the top thanks to a comfortable 2-1 victory away to Chievo, thanks to well-worked goals by Alessandro Matri and Stephan Lichtsteiner.
Fiorentina finally celebrated their first victory of the calendar year with Luca Toni and Stevan Jovetic seeing off Parma.
Lazio fought back from 2-0 down, but were eventually beaten by a Marco Rigoni goal in the dying seconds of this 3-2 Marassi thriller.
Mario Balotelli scored a brace, including a hugely controversial penalty with the last kick of the game, to beat Udinese 2-1 on his Milan debut.
Napoli are top of the table for at least one night, as Marek Hamsik and Paolo Cannavaro gave them a 2-0 victory over Catania.
Palermo debuted a host of new players, but were still beaten 2-1 on home turf by Atalanta despite a late comeback.
Bologna fought back twice to secure a thrilling 3-2 victory in Pescara, a relegation battle with three penalties.
Goals from Radja Nainggolan, Marco Sau and Francesco Pisano, as well as an own goal from Mauro Goicoechea, gave Cagliari a 4-2 win over Roma.
Siena earned a shock 3-1 victory over 10-man Inter, as Cristian Chivu saw red and Innocent Emeghara scored on his full Serie A debut.
Torino and Sampdoria both had chances, but ultimately a goalless draw was the correct reflection of this relegation tussle.