Napoli beat SPAL for a ninth Serie A win in a row – a club record in a single season – to go top again.
Juventus had briefly gone top with a 1-0 win over Torino earlier on Sunday.
Allan gave Napoli the lead after a quick one-touch passing move ended with Jose Callejon playing in the Brazilian.
Marek Hamsik thought he had doubled their lead when he headed in Allan’s cross, but the goal was eventually ruled out for offside after video assistant referee (VAR) consultation.
Hamsik, the club’s all-time top scorer, was then shown a yellow card for breaking the corner flag in his celebrations before the goal was disallowed.
Elsewhere, Cheick Diabate scored an 89th-minute winner on his Benevento debut as they picked up the third Serie A win in their history, by beating Crotone 3-2.