Serie A leaders Juventus suffered only their second league defeat of the season when they were beaten 2-0 at an inspired Napoli.
Striker Jose Callejon and substitute Dries Mertens scored for third-placed Napoli to hand Juventus their first league loss since Oct. 20.
Juve's lead was to cut 11 points after second-placed Roma, who have a game in hand, won 2-0 at Sassuolo earlier today.
Juventus, still firmly on course for a third successive Scudetto, had won their last seven league matches, although the last four of those were by a single goal.