Jose Maria Callejon opened the scoring after just 12 minutes, but Serie A top-scorer Giuseppe Rossi levelled things up from the penalty spot just before the half-hour.
Dries Mertens scored what proved to be the winner in the 36th minute, but there was late drama as Napoli's Cristian Maggio was dismissed 10 minutes from time and Juan Guillermo Cuadrado ensured both sides finished with 10 men in the dying seconds.
Juventus are also two points back after a convincing 4-0 win over Catania.
Arturo Vidal and Andrea Pirlo both scored in the first half with Carlos Tevez and Leonardo Bonucci adding to the score after the break.
Tiberio Guarente was sent off six minutes from time for Catania, but Juve did not add to their tally.
Roma are likely to extend their lead back to five points on Thursday as they defend their 100 per cent record against a Chievo side without a win in five games.
Hellas Verona sit eight points back from the leaders following a 2-0 win over Sampdoria.
Juan Ignacio Gomez Taleb and Luca Toni struck in the second half to ensure Verona kept pace with Inter Milan, who could only draw with Atalanta on Tuesday night.
Kaka was on target for Inter's city rivals AC as they drew 1-1 with Lazio.
The Brazilian opened the scoring nine minutes into the second half, but Michael Ciani ensured a point for the capital side in the 72nd minute.
Alessio Cerci's late equaliser snatched a point for Torino and denied Livorno a remarkable come-from-behind win.
Goals from Ciro Immobile and Kamil Glik had the visitors 2-0 up within eight minutes, but Sergio Paulinho, Leandro Greco and Ramos Emerson had Livorno ahead before Cerci's 87th-minute strike made it 3-3.
Luis Muriel's goal 11 minutes into the second half allowed Udinese to see off Sassoulo 2-1.
Antonio Di Natale put Udinese ahead from the penalty spot before Simone Zaza, who was later sent off, equalised for Sassuolo.
Bologna cruised to a 3-0 win over 10-man Cagliari.
Gyorgy Garics opened the scoring before Nicola Murru was sent off and Panagiotis Kone and Michele Pazienza soon rounded off the win.
In the evening's other game, Alberto Gilardino scored the only goal as Genoa beat Parma 1-0.