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Buffon was called into action again four minutes later when Marek Hamsik latched on to a cross before curling an effort towards goal, but the Juve keeper was equal to it.
Napoli responded with another chance of their own three minutes later as Faouzi Ghoulam's cross from the left found its way to Callejon, whose shot once again kept out by Buffon.
Callejon was not to be denied for much longer, however, as he opened the scoring eight minutes before half time with a close-range finish from another Ghoulam cross.
Juventus looked to pull a goal back before the break through Osvaldo's acrobatic effort, but he couldn't steer his shot on target.
The visitors began to step up the pressure in the second half and had a chance to level things up 10 minutes after the restart when Lichtsteiner found himself in an advanced position, but once again Reina was equal to his effort.
Buffon was soon back in action again, however, palming Ghoulam's fierce free kick over the bar before denying Hamsik's low curling effort from the edge of the box.
Napoli got their crucial second goal with nine minutes left as Dries Mertens made an immediate impact off the bench, latching on to Goran Pandev's pass before drilling his shot past a stationary Buffon.
The visitors could not respond in the closing stages of the match as Napoli held on for three points that edge them within six of second-placed Roma in the table.