Milan: Napoli fell to a surprise 3-0 defeat at Atalanta in the Italian league on Sunday as German Denis struck twice against his former club.
Napoli remained third, 12 points behind leader Juventus, which hosts Inter Milan in the derby d'Italia later.
Rafa Benitez's team is six points behind second-placed Roma, which saw its match against Parma abandoned after eight minutes due to a waterlogged pitch.
At the other end of the table, Catania drew 3-3 at home to Livorno in a tense relegation battle between the two bottom clubs in Serie A.
Sassuolo also remained in the relegation zone after losing 2-1 at home to high-flying Hellas Verona.
Lazio continued its resurgence under Edy Reja as it comfortably beat Chievo Verona 2-0.