Radja Nainggolan hit a first-half winner as Roma edged Udinese 1-0 to close the gap on leaders Juventus to a single point in Serie A on Sunday.

Juventus, bidding for a record sixth straight league title, can restore their four-point lead if they beat Fiorentina away in Sunday's late game.

But the Old Lady of Turin was given another reminder of potential obstacles on the way to the Serie A title with Roma, Napoli, Lazio and Inter all winning.

Roma travelled to the Friuli stadium looking to make it three wins on the trot having suffered their last reverse in a 1-0 defeat at Juventus in December.

The visitors went in front on 12 minutes when Nainggolan turned on Kevin Strootman's chip from deep in midfield to beat Orestis Karnezis with a right-footed volley from eight yards.

Luciano Spalletti's men should have doubled their lead when a penalty was awarded minutes later for handball in the area, but Edin Dzeko ballooned his effort over.

"It's a win that allows us to keep track with the teams below us that also won their games," Spalletti told Radio Rai.

Referring to Dzeko's miss, he added: "The only regret I have is we didn't settle the match earlier."

Juventus are now just a point ahead of Roma although the Turin giants have a game in hand following Italian Super Cup commitments last month. In Doha, the champions were beaten on penalties by AC Milan.

Napoli's last league defeat also came at Juventus, at the end of October, but at home to league strugglers Pescara the Azzurri were kept scoreless until Lorenzo Tonelli, Marek Hamsik and Dries Mertens hit one apiece in a fruitful second half.

Tonelli got the hosts off the mark with his second goal in as many games when he rose to meet Jorginho's free kick from the left to send a bouncing header past Albano Bizarri in the Pescara net.

For Napoli coach Maurizio Sarri, the former Empoli defender's batling qualities were an example to follow.

"He battles more than his team-mates," Sarri told Rai Sport. "And if he can manage to transmit that to the rest, it will stand us in good stead."

Napoli doubled their lead moments later, Hamsik volleying Piotr Zielinski's long ball past Bizzarri from a tight angle.

Lorenzo Insigne then Jorginho came close, but Bizzarri was left helpless in the dying minutes when Mertens completed a one-two with Allan to flick past the 'keeper for his 12th goal of the campaign.

Lazio remain fourth, at five points behind Juventus, after Ciro Immobile's second-half penalty secured the points in a 2-1 win over Atalanta that saw the coaches of both teams, Simone Inzaghi and Gianpiero Gasperini, sent off for dissent after angry exchanges with the referee.

Former Lazio 'keeper Etrit Berisha was out to make a brave stop from the feet of Immobile in the early stages but Atalanta took a 21st minute lead when Andrea Petagna fired a superb volley past Federico Marchetti from Remo Freuler's cross.

Sergej Milinkovic-Savic rose to meet a free kick at the back post to head Lazio's leveller on the stroke of half-time.

When the Serbian was hauled down by Berisha's clumsy challenge after the restart, Immobile stepped up to send the 'keeper the wrong way with his 11th league goal of the season.

Having suffered a fruitless first half, a half-time talk with Lazio coach Inzaghi, did the trick for Immobile.

"I told him to stay calm and he would soon score," said Inzaghi.

"He's a great player for us. Even when he's not scoring, he's creating chances."

AC Milan, in fifth at nine points adrift, are away to Torino on Monday. Inter Milan moved up to sixth with a 3-1 win over Chievo on Saturday when Mauro Icardi hit the opener to stretch his league-leading goals tally to 15 for the season.