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.

Caldara inexplicably coughed up possession just outside his own box, allowing Kvaratskhelia to tee Osimhen up for a tap-in.

If Sunday's Milan derby finishes as a draw, Napoli will end the weekend 15 points clear at the top of Serie A.

Even with the potential distraction of the Champions League still to come, it is difficult to imagine Napoli throwing the title away from this point.

The fact they do not even have to be that good to win is itself an ominous sign for the chasing pack, all of whom have been blighted by inconsistency.

Key men lead from the front

Undoubtedly Osimhen and Kvaratskhelia are the ones spearheading this title push and once again they were decisive.

Kvaratskhelia became only the fifth player across the top five European leagues this season to register at least 10 goals and 10 assists (10 and 12), while Osimhen become just the fourth Napoli player to net as many as 16 times in the first 21 Serie A games of a season.

Caldara endures a nightmare

It was a day to forget for Spezia's centre-back.

He almost scored an own goal, then he was at fault for the final Napoli goal with a bizarre pass straight to Kvaratskhelia.

Additionally, he really struggled to get to grips with Osimhen, with a slight shirt pull by the Nigerian on the defender the only thing preventing Napoli's star striker getting a hat-trick.

Key Opta Facts

Since Spalletti joined Napoli, the Azzurri have kept 25 clean sheets in Serie A, more than any other side, conceding just 46 times.

Spezia have failed to score in four of their last five league games.

Of the players in Europe's top five leagues to have registered 10+ goals and 10+ assists, Kvaratskhelia is the youngest. The others are Lionel Messi, Neymar, Randal Kolo Muani and Serge Gnabry.

Osimhen (19) and Kvaratskhelia (17) are the two players who have been directly involved in most goals in Serie A this season.

Only Erling Haaland (25) has scored more goals than Osimhen (16) in the top five European Leagues this season, while just Harry Kane (seven) has converted more headers than the Napoli number nine.

What's next?

Napoli will be firm favourites in a week's time when they host Cremonese, who still have not won in Serie A this season.