Victor Osimhen was unstoppable with two goals and an assist as Napoli flattened Spezia 4-1, but lost Dries Mertens to injury.

Victor Osimhen curled wide of the far post following a defensive error, but Piotr Zielinski opened the scoring when meeting the Giovanni Di Lorenzo pull-back from six yards.

Spezia tried to fight back with a Nahuel Estevez shot charged down, but it just left them exposed on the counter, with Zielinski sending Osimhen clear from his own half to double their lead. That was the fourth consecutive match on target for the Nigeria international.

The striker’s pace was again decisive, but this time the Spezia defence was caught napping, as Lorenzo Insigne dinked up a free kick and Osimhen sprung the offside trap to chest and volley in undisturbed.

Diego Demme forced a save from close range after an Insigne back-heel flick, while Matteo Politano blasted over after another run from midfield.

Spezia did get one back when Alex Meret made the save on an Estevez diving header, but could do nothing on substitute Roberto Piccoli’s follow-up.

Dries Mertens came off the bench, but lasted only seven minutes before hobbling off with an ankle injury.

Napoli’s fourth goal was initially disallowed, but Osimhen was onside when he started his run again from the centre-circle, although this time he generously rolled it across for Hirving Lozano to tap in instead.