MILAN — Who needs Gonzalo Higuain, the record goalscorer in Serie A, when you have Dries Mertens?

Mertens' emergence has eased the pain caused by Higuain's departure in the off-season. Not content with bagging a hat trick last weekend, the diminutive forward netted four on Sunday to help Napoli to a 5-3 win over Torino.

Mertens completed a hat trick in nine first-half minutes and then saved the best until last — a sublime chip into the far corner in the 80th minute.

"Mertens is an extraordinary player, but the team makes it easier for him with the type of football they are playing," Napoli coach Maurizio Sarri said. "But we have to grow mentally. It should have been a match that was definitively over once we went 3-0 up and it wasn't.

"We conceded goals with three stupid mistakes, carelessness that we absolutely can't commit, but it was a very high level performance."

Napoli leapfrogged above AC Milan into third, a point behind second-place Roma. It can be joined on 34 points by Lazio if the capital team beats Fiorentina later.

Higuain transferred to Juventus for an Italian-record 90 million euros ($100 million) after breaking a 66-year-old Serie A record with 36 goals for Napoli last season.

Arkadiusz Milik was signed to replace him and scored seven goals in eight matches, but tore the anterior cruciate ligament in his left knee while playing for Poland in October.

As a result, Sarri has been relying on a three-man forward line with Lorenzo Insigne and Jose Callejon flanking Mertens — and the trio is starting to gel.

Napoli opened the scoring in the 13th minute. It had taken short corners many times this season but to little dividend. However, this time it worked as it was played for Callejon, who crossed for Mertens to fire in on the bounce.

Mertens doubled his tally five minutes later, winning and converting a penalty after being pushed over by Antonio Barreca.

The 29-year-old forward completed his second successive hat trick in the 22nd minute.

Torino goalkeeper Joe Hart did brilliantly to keep out a powerful shot by Callejon, only for Mertens to fire in the loose ball at the second attempt after his initial effort was cleared off the line by Luca Rossettini.

Andrea Belotti got Torino back into the game shortly before the hour. It was the Italy forward's 12th league goal of the season and moved him level with Inter Milan forward Mauro Icardi and Roma's Edin Dzeko at the top of the scoring charts.

Napoli restored its three-goal advantage in the 70th when Callejon rolled a low cross across face of goal and Vlad Chiriches tapped it in at the far post.

Torino again reduced the deficit when Pepe Reina spilled Adem Ljajic's free kick and Rossettini was on hand to prod it in. But Mertens scored his fourth four minutes later.

Iago Falque converted a penalty in the 84th for Torino.

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LAZIO 2, FIORENTINA 1

Lazio continued its good run of form as it moved level on points with Napoli in third place, while Fiorentina fell to its second successive defeat.

Lazio took the lead in the 23rd minute with a well-worked move. Sergej Milinkovic-Savic collected Felipe Anderson's through-ball before passing it on for Keita Balde Diao to sweep into the far corner of the net.

Lucas Biglia doubled Lazio's lead with a penalty in first-half stoppage time after Nenad Tomovic bundled over Milinkovic-Savic.

Fiorentina should have got back into the match immediately after halftime but Lazio goalkeeper Federico Marchetti saved Josip Ilicic's penalty after Biglia had fouled Sebastian Cristoforo.

It did pull one back in the 64th minute through substitute Mauro Zarate, who had only been on the pitch a few minutes.

Fiorentina thought it had levelled seven minutes from time but the goal was ruled out for handball and any thoughts it had of snatching a point evaporated when Stefan Radu sealed the result.

Fiorentina slipped to eighth and faces Napoli on Thursday in its final match before the winter break. Lazio visits Inter Milan on Wednesday.

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GENOA 3, PALERMO 4

Palermo remarkably fought back from two goals down in the second half to end a run of eight successive defeats.

Robin Quaison's brilliant solo goal for Palermo cancelled out Giovanni Simeone's opener to leave it all even at the break.

Simeone, the son of Atletico Madrid coach Diego Simeone, headed in a second and also set up Genoa's third for Nikola Ninkovic in the 65th.

But Edoardo Goldaniga pulled one back for Palermo four minutes later and Andrea Rispoli levelled two minutes from time. Genoa players were furious as Rispoli appeared to be offside.

Genoa pushed forward for the winner but it was Palermo that snatched all three points as Aleksandar Trajkovski finished off a counter attack.

Genoa goalkeeper Mattia Perin was sent off for pushing Ilija Nestorovski over when the forward tried to delay a free kick in stoppage time, completing a miserable night for the hosts.

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OTHER MATCHES

Inter Milan is finding its feet under new coach Stefano Pioli and won 1-0 at Sassuolo for its fourth win in five matches — between Serie A and Europa League.

Antonio Candreva scored the only goal of the match two minutes into the second half. Inter midfielder Felipe Melo was sent off in stoppage time for a second bookable offence.

Bologna ended its goalscoring drought by winning 3-0 at 10-man Pescara, which played with 10 men for an hour after Valerio Verre was sent off for a dangerous tackle.

Elsewhere, Chievo Verona beat Sampdoria 2-1 and Cyril Thereau scored twice as Udinese beat Crotone 2-0.