With a four-point cushion on Fiorentina and Napoli before the final Serie A games of 2015, Inter Milan will start the New Year top of the pile irrespective of their result against Lazio in Sunday's later clash.
But Roberto Mancini's men were given a reminder of what lies ahead in the second half of the season after Napoli, Fiorentina, Roma and Juventus all won their respective final games before the league takes a two-week break.
Juventus had moved up to second earlier with a patchy 3-2 win at Carpi that gave the champions their seventh consecutive victory as they continue to make amends for a disastrous start to the campaign.
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Massimiliano Allegri's men are now fourth, at three points behind Inter and two behind Fiorentina and Napoli, following respective wins for the pair.
In Florence, Nikola Kalinic broke the deadlock in the 20th minute with an angled shot that squirmed under Albano Bizzarri's legs.
Strike partner Josip Ilicic doubled Fiorentina's lead with a fine dipping strike from outside the area that beat Bizzarri at the 'keeper's far post to wrap up the points for Paulo Sousa's hosts.
Atalanta, who stunned Roma 2-0 in the Italian capital a fortnight ago, had pledged to make life hard for Napoli in Bergamo and for a time the visitors toiled.
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But seven minutes after the restart Napoli captain Marek Hamsik fired in off the crossbar to beat Davide Bassi from the penalty spot after Dutch defender Marten De Roon handled a cross floated in for Higuain.
Atalanta pulled level two minutes later thanks to Alejandro Gomez's low strike, only for Higuain to restore the visitors' lead with a flicked-on header that beat Bassi at the keeper's near post.
The Argentinian celebrated stretching his league-leading tally to 15 goals by running half the length of the pitch to hug coach Maurizio Sarri, who has been credited with Napoli's title push this season.
Higuain later told Sky: "Few teams have come here and played well, but we did -- you can see from the result.
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"I'm happy for the goals, I'm working hard and if I'm feeling good then it's all down to the coach, to the club and to my teammates."
Napoli's Brazilian midfielder Jorginho saw red for a studs-up challenge, but Higuain put the result beyond doubt when he powered down the right and held off his marker to beat Bassi with an angled strike.
Hamsik spurned a late chance to make it four, firing a second penalty over after Gabriel Paletta had been sent off for pulling down Dries Mertens as he was about to pull the trigger in front of goal.
Edin Dzeko was sent off for dissent in the second half at the Stadio Olimpico, where Alessandro Florenzi's close-range volley gave the embattled hosts a 42nd minute lead against Genoa.
But 18-year-old Umar Sadiq, who replaced Mohamed Salah eight minutes from the end, eased any late nerves when he ghosted in at the back post to head past Mattia Perin to score his maiden Serie A goal and spark wild Roma celebrations.
The 2-0 win ended a four-game winless streak for Rudi Garcia's men, who remain in fifth spot at four points behind Inter and one behind Juventus.
Florenzi followed his goal by hugging under-fire Garcia, who said afterwards: "Of course we're emotional, but it shows how important it was for us to give it everything tonight to try and win this game.
"We went down to 10 men for the last 15-20 minutes, so the lads deserve all the credit for holding on and coming up with the second goal. Sadiq is learning his trade from some of the top players in the league."
Inter will restore their four-point advantage later Sunday if they overcome a struggling Lazio side at the San Siro.
Lazio are on a seven-game winless run that has dropped them to 12th place at 16 points behind Inter.
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