Napoli moved into fourth place in Serie A after goals from Marek Hamsik and Edinson Cavani at Lecce kept their prospects of Champions League football alive.
The visitors scored at the start of either half to go within a point of third-placed Lazio, who surprisingly lost at Novara, while Udinese also slipped up at home to Inter Milan.
Hamsik handed his side the lead in the fifth minute, with Cavani doubling the lead six minutes after the break as Lecce failed to make their own chances count.