Khvicha Kvaratskhelia and Victor Osimhen ruthlessly punished three defensive errors as Napoli beat Spezia 3-0 to increase their lead at the Serie A summit to 16 points.
Luciano Spalletti's side may not have been at their swashbuckling best but produced a professional display at Stadio Alberto Picco on Sunday and never looked at risk of dropping points once they edged in front.
An uneventful first half brought few clear-cut chances, but Napoli took charge of the contest just a minute into the second, with Kvaratskhelia coolly converting a penalty.
Another mistake allowed Osimhen to score for the fifth league game in a row, and he netted again soon after as Spezia proved to be their own worst enemies.
Both sides looked purposeful early on, with Kevin Agudelo threatening first as he blazed over following a driving run.
Mattia Caldara then chested a Mario Rui cross just wide of his own goal at the other end, and from the subsequent corner Giovanni Di Lorenzo went agonisingly close with a glancing header.
Proceedings soon calmed significantly, but Spezia gifted Napoli the breakthrough via a penalty concession a minute after the restart.
Arkadiusz Reca blatantly handled the ball in the box and Kvaratskhelia slammed home his spot-kick.
Osimhen was then on hand to capitalise on Ethan Ampadu's sliced clearance with 68 minutes played, nodding in above Dimitris Nikolaou and Bartlomiej Dragowski.
The two goalscorers linked up five minutes later to finish Spezia off.