Napoli missed the chance to keep pressure on Serie A leaders Juventus by losing 3-1 at Udinese on Sunday, with a meltdown by striker Gonzalo Higuain potentially decisive in the title race.
After Juventus beat Empoli 1-0 on Saturday, Napoli could not afford to drop points at Stadio Friuli but Maurizio Sarri's side fell behind to an opening goal by Bruno Fernandes.
Higuain levelled the scores with his 30th league goal of the season, but within a minute Fernandes had a chance to restore the lead, only for Gabriel to save his penalty, although the Portuguese midfielder made amends with a bicycle kick before half-time to restore the hosts' lead.
Cyril Thereau volleyed in Udinese's third before Higuain was dismissed for a second yellow card, after which he pushed referee Massimiliano Irrati in the chest, which could earn the Argentina international a lengthy suspension.
Roma maintained their grip on third place and closed the gap to Napoli to four points with a 4-1 victory in the Rome derby against Lazio, who sacked Stefano Pioli due to the defeat against their rivals.
Stephan El Shaarawy put Luciano Spalletti's side into the lead and Edin Dzeko hit the second before Marco Parolo got one back for Lazio.
But goals from Alessandro Florenzi and Diego Perotti, the first a fine volley, secured victory for Roma, while Lazio's Wesley Hoedt was sent off deep in injury time.
Fiorentina were held 1-1 at home to Sampdoria, a result that leaves the former seven points behind Roma in the race for Serie A's final Champions League place.
Inter suffered a 2-1 loss to Torino and had Miranda and Yuto Nagatomo sent off, Andrea Belotti scoring the winner from the penalty spot to leave Roberto Mancini's side in fifth place, hurting their slim Champions League qualification hopes.
AC Milan lost 2-1 at Atalanta on the day club great Cesare Maldini died, Mauricio Pinilla and Alejandro Gomez scoring after Luiz Adriano's early opener.
Palermo and Frosinone remain in the Serie A relegation places after suffering a 3-1 loss at Chievo and a 4-0 defeat at Genoa respectively, with Suso hitting a hat-trick in Genoa's win.