Dries Mertens scored his first league goal since October as Napoli maintained their Serie A title challenge thanks to a 1-0 win at Atalanta.
Maurizio Sarri's men went into the game a point ahead of second-placed Juventus - who host Genoa on Monday - having won their last four in the league and, although it was by no means a comfortable outing, Mertens made the difference in the second half.
The first period passed with little excitement, as the two sides generally cancelled each other out in midfield and neither managed to get a shot on target.
One of very few first-half flash points involved Lorenzo Insigne, as the forward reacted to the crowd for jeering him when injured, appearing to whistle and gesticulate back in the direction of the stands.
After the break, Napoli looked more potent in attack and nearly went ahead early on with Jose Callejon's header partially stopped by Etrit Berisha, before Andrea Masiello cleared off the line.
But there was to be no denying Mertens just after the hour mark, the Belgian unleashing a fierce half-volley to end a run of 910 minutes without a league goal.
Marek Hamsik missed a late chance and saw another goal disallowed for offside, but it mattered little as they held on to go four points clear, at least until Monday.