A late Lorenzo Insigne goal rescued a 1-1 draw for second-placed Napoli at Sassuolo in Serie A on Sunday but it was not enough to stop them losing further ground on runaway leaders Juventus.
Juve finished the weekend with an 18-point lead following a 4-1 home win over Udinese on Friday and with 11 games to play are 15 points from clinching their eighth successive title.
Napoli, involved in the Europa League round of 16, rested a number of players and also had goalkeeper Alex Meret suspended.
Sassuolo went ahead seven minutes after halftime when Domenico Berardi turned in Jeremie Boga's pass from close range.
Napoli appeared to be heading for a fifth league defeat of the season until Insigne pounced on a mistake in the Sassuolo defence and curled the ball in with four minutes left.
Unbeaten Juventus, who have won 24 of their 27 games and drawn three, have 75 points with Napoli on 57.