Inter's Serie A title hopes suffered a serious blow when the defending champions suffered a 1-0 home defeat by Roma, giving Napoli the chance to extend their three-point lead at the top when they host Torino later on Sunday.
Inter, who were eliminated from the Italian Cup on Wednesday after a 3-0 semi-final defeat by Milan, suffered their third defeat in a week.
Roma took the lead at the "San Siro" in the 22nd minute through Matthias Sule, and Inter could not find a way back into the game and suffered a second consecutive league defeat after a 0-1 defeat at Bologna last Sunday.
Inter, who need to recover before Wednesday's Champions League semi-final first leg against Barcelona, are second in the standings, level on 71 points with leaders Napoli, while Roma climbed to fifth place with 60 points.
In another league match, Fiorentina won 2-1 against Empoli. In the 7th minute, Yacine Adli put the hosts ahead, and in the 25th minute, Rolando Mandragora made it 2-0 with a beautiful strike. Jacopo Fazzini was on target for the visitors in the 57th minute. Fiorentina, who are unbeaten in nine Serie A matches, are eighth in the standings with 59 points. Empoli with 25 points is in the penultimate, 19th place.
Later today Juventus hosts Monza, Atalanta hosts Lecce, and Napoli hosts Torino.