Lozano scored twice while Piotr Zielinski, Mertens, ELif Elmas and Matteo Politano also found the back of the net for the Partenopei.
The match was originally scheduled for 15:00 local time but was moved three hours later after Grifone players Mattia Perin and Lasse Schone tested positive for COVID-19.
The Partenopei took the lead after 10 minutes when Mertens crossed from the left-wing with his right foot, Lozano ran in, and his first shot crossed the line despite the efforts of Marchetti. For good measure, the Napoli winger kicked the rebound back into the net.
Osimhen squandered two opportunities to extend the Partenopei’s lead, while Grifone wing-back Davide Zappacosta squeezed in an effort of his own in between, only for the shot to go wide.
Lozano nearly scored his second after Mertens found him making a late run into the box but the Mexican international shot tamely across goal. Unfortunately for Napoli, their captain Lorenzo Insigne had to come off the field with an injury after 20 minutes and he was replaced by Elmas.
Osimhen missed another chance to score for the Neapolitan side, and the Grifone still created chances to level through Zappacosta and Miha Zajc, but they could not hit test Alex Meret in the Partenopei goal.
With half time nearing, Osimhen persisted with his efforts to find his first Serie A goal yet another one of his shots went off target.
Napoli commenced the second half with a bang after Zielinski ran from his own half, passed to Elmas, and then Osimhen laid the ball off to the Polish international, who continued his run and beat Marchetti.
Marchetti had to be alert and he was quick enough to deny Elmas and then Mertens to extend the Ciuciarelli’s lead while Giovanni Di Lorenzo also headed wide.
After an error in midfield by Lerager, Mertens ran onto a pass to score Napoli’s third after 57 minutes, effectively ending the game as a contest.
Mertens turned provider for Lozano again and the Mexican made it 4-0 to the Neapolitans in the 64th minute. Five minutes later, Elmas added the fifth after running onto Elseid Hysaj’s pass and beating a defender.
Napoli kept running riot, and Politano made it 6-0 after beating Edoardo Goldaniga, then putting the ball into the bottom far corner.
For the remainder of the match, the Partenopei maintained possession without exerting too much energy and with little resistance from the Rossoblu.