A splendid Giacomo Raspadori free kick midway through the first half was enough for Napoli to defeat Lecce and make it four wins on the spin.
After Romelu Lukaku had seen an early goal ruled out for a fractional offside, Jack stepped up and curled into the bottom corner from the edge of the box to give us the lead.
Lecce then hit the bar and Raspadori had another effort run just the wrong side of the post as the first half ended 1-0.
Napoli produced a controlled display in the second half to claim a crucial three points.
The result means they remain top of the table with three matches left to play.
Lecce 0-1 Napoli (HT 0-1)
Scorer: Raspadori 24.
LECCE: Falcone; Guilbert (Veiga 63), Gaspar, Baschirotto, Gallo, Coulibaly, Pierret (Berisha 66), Kaba (Morente 46), Pierotti (N'Dri 84), Karlsson (Helgason 46), Krstovic.
Coach:. Giampaolo.
NAPOLI: Meret; Di Lorenzo, Rrahmani, Olivera, Spinazzola; Politano (Ngonge 87), Anguissa, Lobotka (Gilmour 54), McTominay, Raspadori (Billing 79), Lukaku (Simeone 87).
Coach: Conte.
Referee: Massa (Imperia)
Booked: Morente, Krstovic.
