Scott McTominay scored the only goal after just two minutes as Napoli moved second in Serie A on Friday with a 1-0 win at Cagliari.
Antonio Conte's side closed to within six points of Inter Milan, before the league leaders play at Fiorentina on Sunday.
Napoli are now two points clear of third-placed AC Milan, who play at home against Torino on Saturday.
Scotland midfielder McTominay was starting his first match since 7 February after a tendon problem, but tapped the ball into the empty net after it had bounced between goalkeeper Elia Caprile's legs.
Conte could also count on the return of Belgian midfielder Kevin De Bruyne, who started for Napoli for the first time since being forced off with a leg injury on 25 October against Inter.
Cagliari's Sebastiano Esposito fired wide as the hosts missed the chance to level after 20 minutes, with Napoli's Leonardo Spinazzola also clearing the ball off the line to prevent a late equaliser before the final whistle.
Napoli created numerous chances but failed to convert them as they held their narrow advantage until the end against the 15th-placed Sardinian side.