MILAN (AP) -- 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 Hellas Verona, which snapped a run of three successive defeats.
Lazio continued its resurgence under Edy Reja as it comfortably beat Chievo Verona 2-0.
Napoli instigated its own downfall in Bergamo as a series of defensive howlers led to a crushing defeat.
Atalanta broke the deadlock less than two minutes after halftime. Blerim Dzemaili gave the ball away in midfield and Denis' powerful drive from outside the area bounced under the diving Napoli goalkeeper Pepe Reina.
Denis -- who spent four years at Napoli -- doubled his tally in the 65th minute when he latched onto a poor attempted clearance from Gokhan Inler and fired across into the bottom left corner.
Maxi Moralez sealed the result five minutes later following another error from Federico Fernandez.
Roma's match against Parma was abandoned after only eight minutes' play, with the score at 0-0.
Bottom club Catania remained two points behind Livorno after an entertaining draw, which helps neither club in the relegation battle.
Catania fought back from a goal down three times as Innocent Emeghara scored twice for Livorno, which also had a penalty converted by Paulinho.
Gonzalo Bergessio and Pablo Barrientos scored for Catania, and the home side leveled for the third time in the final minute when substitute Sergio Almiron was left unmarked at the far post to control and fire in a cross.
Livorno moved level on points with Sassuolo after new coach Alberto Malesani's debut ended in defeat against his former club.
Verona broke the deadlock five minutes into the second half when Tomas Manfredini turned Emil Hallfredsson's cross into his own net at full stretch as he attempted to prevent the ball reaching Luca Toni.
Toni all but sealed the match three minutes from time when he beat the offside trap and chipped the onrushing goalkeeper Gianluca Pegolo.
Antonio Floro Flores headed home Domenico Berardi's free kick in stoppage time for a consolation goal for Sassuolo.
Lazio has not lost since Reja replaced Vladimir Petkovic.
It took six minutes for the capital side to take the lead against lowly Chievo as Antonio Candreva fired in Keita Balde's cross.
The 18-year-old Balde capped an impressive performance by scoring Lazio's second, when his effort was deflected into the near corner.