Gonzalo Higuain scored his 30th league goal of the season but was later sent off and had to be restrained by his team mates as Napoli lost 3-1 at Udinese on Sunday, severely denting their Serie A title hopes.
The Argentine appeared to push referee Massimiliano Irrati in the chest after being shown his second yellow card in the 75th minute and, overcome with rage, lashed out at team mates and Napoli officials as they ushered him off the field.
Midfielder Bruno Fernandes converted one penalty, missed another and scored with an overhead kick for Udinese while Napoli dropped six points behind leaders Juventus, who beat Empoli 1-0 on Saturday, with seven matches to play.
AS Roma thumped Lazio 4-1 in the Rome derby, which for the second time this season was played in a half-empty Stadio Olimpico as fans protested over security measures.
AC Milan, a modest sixth, suffered a fresh setback as they lost 2-1 at Atalanta where Mauricio Pinilla scored with a trademark bicycle kick for the hosts.
Higuain, whose second yellow card was given for what appeared to be an innocuous challenge on Felipe, may now face a lengthy ban which could prove fatal to Napoli's hopes of a first title since 1990.
Napoli also had coach Maurizio Sarri sent off for dissent after the second penalty award in the first half and he watched the game from the stands, quietly smoking.
"I just told Irrati that he was refereeing really badly, but you can't even say that," Sarri told reporters.
Udinese went ahead after 14 minutes when Fernandes converted a penalty with a shot which went under Gabriel's arms as the Napoli goalkeeper dived to his right.
Higuain equalised 10 minutes later with a piledriver of a shot but Udinese were given another penalty almost immediately after Faouzi Ghoulam tripped Silvan Widmer.
Fernandes again sent the ball to Gabriel's right but this time the Brazilian goalkeeper, standing in for the injured Pepe Reina, saved the shot.
Gabriel turned villain, however, in first-half stoppage time when he lost control of the ball and chased Duvan Zapata out of the area. The Colombian crossed into the centre and Fernandes turned the ball into an empty net with a bicycle kick.
Cyril Thereau volleyed the third goal just before the hour as the Napoli defence was caught napping.
Juventus have 73 points, followed by Napoli on 67 with Roma a further four behind in third, the Champions League playoff spot. Fourth-placed Fiorentina (56) lost further ground when they drew 1-1 at home to Sampdoria.
