Scott McTominay ed Napoli from Manchester United in August after 22 years at Old Trafford
Juventus and Napoli both missed the chance to move to the top of Serie A after a goalless draw in Turin.
The scrappy stalemate at the Allianz Stadium meant Torino, 3-2 winners over Hellas Verona on Friday, remained at the summit.
Scotland midfielder Scott McTominay went close just before the half hour for Napoli with a shot from the edge of the box which was saved by Michele di Gregorio.
The Juventus goalkeeper was also called into action again on the stroke of half-time when he tipped away Matteo Politano's free-kick.
Politano then fired over the crossbar from 18 yards for Antonio Conte's side early in the second half, while Teun Koopmeiners curled over from a good position for Juve.
Napoli moved up to third place on 10 points - a point behind Torino and one clear of Juve who are fourth after their third successive league draw.
Inter Milan face city rivals AC Milan at San Siro on Sunday (19:45 BST) in the weekend's big clash in Italy.
