Inter Milan opened up a six point lead at the top of the Serie A table after a hard fought 2-1 victory against Napoli at the San Siro on Sunday.
City rivals AC Milan can cut the gap back down to three points, though, if they win at Palermo in the day's late game.
As Roma continued their recovery with a narrow 1-0 home victory over Fiorentina, their third straight success in the league.
On paper Napoli looked to be a tough test for Inter but the champions seemed to be strolling away with the game midway through the first period as they opened up a 2-0 lead.
Napoli gifted their hosts a 16th-minute advantage with poor defending at a short corner which was played to Sulley Muntari who crossed for Colombian centre-back Ivan Cordoba to volley home on the turn.
Inter's second was pure class, though, as Julio Cruz's backheel presented Maicon with space to shoot inside the box. He scuffed his effort but it arrived at Muntari's feet on the edge of the six-yard box and the Ghana midfielder reacted quickly to flick it between his legs and past the helpless Gennaro Iezzo on 25 minutes.
Nine minutes before the break the visitors fashioned a brilliant goal of their own.
Ezequiel Lavezzi cut in from the right flank and played the ball into Uruguayan Marcelo Zalayeta who, with his back to goal, back-heeled the ball past a line of blue and black shirts.
Argentina forward Lavezzi had continued his run and found himself clean through before cleverly dinking the ball over Julio Cesar as the Brazilian goalkeeper dived at his feet.
The second half was a cagey affair with Napoli lacking the confidence to throw caution to the wind and Inter seemingly content to sit on their lead.
Zlatan Ibrahimovic had a shot well saved for the hosts and captain Javier Zanetti burst through a gap late on but was denied by Iezzo's body.
Napoli came closest when Lavezzi sent a dangerous cross from the right into the box but Cristian Maggio hadn't gambled and the ball travelled through to Julio Cesar.
It was a fifth straight league win for Inter, who responded well to the midweek Champions League defeat at home to Panathinaikos.
Napoli remain fourth as a host of teams failed to capitalise on their slip up.
One of those was Fiorentina who went down to a goal from Roma captain Francesco Totti just before the hour mark.
The capital-based club may be down in 14th place but are now only seven points behind Napoli and a Champions League qualification finish is looking a real possibility despite their early season troubles.
As well as Fiorentina missing out on moving into the top four, Lazio lost 2-0 at Atalanta, Genoa drew 1-1 at home to Bologna and 10-man Udinese fell 1-0 at home to rock bottom Chievo.