Debutant Lorenzo Tonelli scored deep into stoppage time as third-placed Napoli came from a goal behind to defeat 10-man Sampdoria 2-1 in Serie A.

Matias Silvestre's controversial red card proved a turning point, as the lead given to the visitors by Elseid Hysaj's own goal after 30 minutes evaporated under intense pressure.

Napoli – who had scored 16 goals in their previous four league matches – had been wasteful in front of goal, with Dries Mertens particularly guilty.

But Silvestre's dismissal just after the hour-mark for two quick bookings, the second of which came after he made minimal contact with goalkeeper Pepe Reina, gave the hosts renewed impetus.

Substitute Manolo Gabbiadini turned in Jose Callejon's cutback from a couple of yards to level it up after 77 minutes and the winner arrived with 20 seconds remaining of the five added minutes.

Tonelli – who joined from Empoli in May, but was at first injured and then overlooked by boss Maurizio Sarri – showed Mertens how it is done, blasting home from the heart of the penalty area from fellow defender Ivan Strinic's pass.

It leaves Sampdoria winless on the road since their opening league match, with Marco Giampaolo's side remaining in the bottom half.