Napoli moved into second place in Serie A with a 2-0 win at struggling Venezia on Sunday, as the gap between the top three teams was cut to a single point.
Goals from Victor Osimhen and Andrea Petagna in the second half ensured that Luciano Spalletti's side took advantage of a rare slip-up by league leaders Inter Milan, who lost 2-1 to AC Milan on Saturday.
Napoli are second with 52 points, ahead of third-placed AC Milan on goal difference and one point behind champions Inter, who they face next in Naples on Saturday.
"Nobody thinks it will be easy, but I think that by all pulling in the same direction we can reach our objectives. We have a lot of (objectives), and one is to win the league. Step by step, with determination, we can do it," Osimhen said.
The race for the top four was blown wide open as fourth-placed Atalanta suffered a shock 2-1 defeat at home to Cagliari, who climbed out of the relegation zone for the first time since September.
Gian Piero Gasperini's side went behind through a Gaston Pereiro strike before goalkeeper Juan Musso was sent off, and Pereiro scored again to win it for the Sardinians four minutes after Jose Luis Palomino had equalised.
Atalanta are one point above Juventus, who face Hellas Verona later on Sunday, while Lazio and AS Roma are lurking four points behind the Bergamo club.
Elsewhere, Sampdoria thrashed midtable Sassuolo 4-0 to go five points clear of the relegation zone, and Bologna drew 0-0 with Empoli in a clash between 13th and 11th.