Napoli ceded control of the Serie A title race to reigning champions Juventus after failing to beat Inter Milan at San Siro.
Maurizio Sarri's Azzurri led the table by a point on Sunday morning but were deposed when Juve defeated Udinese 2-0 in the afternoon.
Three points from their evening trip to Milan would have restored their status as front-runners for the Scudetto, which they have not won since 1990, but ambitious Inter held firm to force a goalless draw.
Napoli could even find themselves four...
Lautaro Martinez's move from Racing di Avellaneda to Inter Milan is "99 percent done," according to the Argentine forward's agent Rolando Zarate.
Martinez has scored eight goals in 12 Superliga Argentina matches this season, while his hattrick helped Racing defeat Cruzeiro 4-2 in their opening Coppa Libertadores group game last month.
Inter want him to join Mauro Icardi in their attack next season and Zarate said the deal is as good as signed and sealed.
"The departure of Lautaro to Inter is 99...