Napoli fell 18 points adrift of Serie A leaders Juventus with a 2-1 defeat at Empoli that edged the reigning champions closer to an eighth successive title.
With only eight remaining fixtures for the division's two leading teams, first place will be beyond Napoli's reach if Juve can secure a further seven points.
They retain a seven-point advantage over third-placed Inter, but appear in little more than a battle for second.
Victory took struggling Empoli out of the bottom three and up to 17th, strengthening their hopes of survival. They took the lead through Diego Farias, and while Piotr Zielinski levelled before half-time, Giovanni di Lorenzo scored in the second half to secure a home victory.
Mauro Icardi scored on his first Inter appearance in almost two months as they won 4-0 at 10-man Genoa.
The Argentinian had not played since being stripped of the captaincy in February amid difficult contract negotiations, but returned to training last week.
Roberto Gagliardini had already given Inter the lead when Icardi won and then scored a penalty as Cristian Romero was sent off. Second-half goals from Gagliardini and Ivan Perisic furthered their advantage, leaving Genoa 11th.
Roma dropped points in their pursuit of Champions League qualification after they were held to a 2-2 draw at home to Fiorentina.
They twice trailed to goals from German Pezzella and Gerson, but were brought level by Nicolo Zaniolo and Diego Perotti, which keeps Claudio Ranieri's side seventh in the table but level with Lazio, Atalanta and Torino on 48 points.
The latter are eighth, having won 2-1 at home to Sampdoria after two first-half goals from Andrea Belotti. Manolo Gabbiadini scored for the ninth-placed visitors.
Lazio lost ground when losing 1-0 at SPAL, courtesy of Andrea Petagna's 89th-minute penalty. The hosts sit 15th.
Frosinone won 3-2 at home to Parma after a penalty scored in the 13th minute of second-half stoppage time, but remain 19th and eight points from safety.
Andrea Pinamonti and Luca Valzania scored for Frosinone but 13th-placed Parma twice levelled through Antonino Barilla and Fabio Ceravolo before Daniel Ciofani's late penalty.