Three defensive howlers helped Atalanta claim a resounding 3-0 home victory over Serie A title challengers Napoli at the Stadio Atleti Azzurri d'Italia.
Bergamo has been an inhospitable venue for Napoli over recent years and a brace from German Denis preceded Maxi Moralez's late goal to condemn the southerners to a fifth defeat from their last eight league games here.
More pressing than the fact Jose Reina, Gokhan Inler and Federico Fernandez each made glaring errors to facilitate Atalanta's goals is the fact that Napoli missed an opportunity to catch up with league leaders Juventus and second-placed Roma, who are eight and six points better off respectively.
Daniele Baselli was first to threaten the Napoli goal, his left-footed effort whistling just over the bar, and Cristian Raimondi soon set Giacomo Bonaventura up to unleash a wayward volley past Reina's posts.
Bonaventura continued to menace Rafael Benitez's men but saw his fierce drive blocked by Fernandez before he nodded Moralez's cross just wide of the mark.
Reina was forced to rush off his line to sweep the ball off Moralez's feet as Atalanta pushed ever forward.
Napoli then decided to wake up, Dries Mertens testing Andrea Consigli's reflexes with a shot on the turn before Stefano Lucchini got across to cover Blerim Dzemaili's long-range sighter.
There would be four additional minutes played in the first half but all Napoli could muster was a tentative attempt from Mertens that Consigli neutralised with ease.
Shortly after the restart, Atalanta scored their first goal.
Reina should have coped much better with Denis' powerful strike but the Spaniard instead allowed the ball to slip off his gloves and end up in the net.
Bonaventura - behind all of Atalanta's best moves in the first half - impressed once again as he shrugged off Fernandez's challenge to pick out the onrushing Denis.
Raul Albiol got across the box to close the Argentinian down just in time.
Napoli missed a great chance to equalise on the hour mark as Mertens hesitated in possession having been put clean through on goal by Goran Pandev, and it was clear Benitez needed to switch things around.
He did so by introducing Gonzalo Higuain for Duvan Zapata and the former Real Madrid player soon made his presence felt as he forced a low save from Consigli.
Unfazed, Atalanta doubled their advantage, thanks to another individual error.
This time it was Inler whose lapse in concentration saw him pass straight to the lurking Denis and the ex-Napoli man gratefully clipped the ball past Reina with his right boot.
Five minutes later Atalanta put the game to bed with a third goal.
Once again a glaring defensive mistake let the Orobici have free reign in the final third and, after Fernandez slipped over at a crucial moment, Moralez rounded Reina to shoot high into the net.