Edy Reja’s side, Italy’s surprise packages this season having flirted with relegation last term, had lost last weekend’s city derby with AS Roma and the midweek game at promoted Cesena but were quickly back to their best.
Argentine Zarate appeared to use an arm when he grabbed the opener on 15 minutes before fellow striker Sergio Floccari doubled the lead in the second half from a Zarate assist.
“All of us had the feeling that he moved the ball forward with a hand but soccer is like this, such episodes are crucial,” Napoli coach Walter Mazzarri told Sky after the early game.
Third-placed Napoli, who hit the bar through Ezequiel Lavezzi, had seen the game as a key test for their title credentials but failed to impose themselves.
Trouble between two of Serie A’s most fanatical fanbases was feared at the Stadio Olimpico but never really materialized.
Sampdoria drew 0-0 with Chievo to slip to 10th after again missing the influence of forward Antonio Cassano, dropped by the club for swearing at the president and facing an arbitration hearing soon on his future at the Genoa-based side.
Samp have scored once in five games since his suspension.
Argentina playmaker Javier Pastore increased his burgeoning worth with three goals in seventh-placed Palermo’s 3-1 win over Catania in the Sicilian derby.
Early season strugglers Udinese continued their surge up the table and are level with Palermo and Genoa, who won 1-0 at Cagliari, after last term’s league top scorer Antonio Di Natale bagged a first half hat-trick in a 4-0 home romp over Lecce.
Bari stayed bottom after a 1-0 home loss to improving Parma while Bologna overcame promoted Brescia 1-0.
Fourth-placed Juventus moved level with Inter after a 1-1 draw with Roma on Saturday when Fiorentina beat Cesena 1-0.
Arsenal move up to second after win at Everton
In London, goals from Bacary Sagna and Cesc Fabregas gave Arsenal a 2-1 win at Everton on Sunday to lift them above Manchester United into second place in the Premier League.
Full back Sagna, with only his second goal for Arsenal in over 140 matches, opened the scoring when he fired past Tim Howard at the near post after 36 minutes and Fabregas added the second three minutes into the second half.
Arsenal, who thrashed Everton 6-1 win at Goodison Park on the opening day of last season, dominated for much of the game but had to hang on at the end after Tim Cahill scored for Everton in the dying minutes.
Chelsea lead the standings with 28 points, with Arsenal on 26 and United third on 25 following their 2-2 draw at Aston Villa on Saturday.
