Juventus, who have won seven and drawn one of their last eight meetings with Torino, have 65 points from 25 games while Napoli were on 63 ahead of their game.
Higuain's match came to an end 15 minutes in, the striker deciding he was not able to continue having apparently hurt his ankle after hurdling goalkeeper Salvatore Sirigu.
Juventus have suffered yet another injury blow after Gonzalo Higuain was forced off in the Turin derby, potentially throwing his participation against Tottenham Hotspur into doubt.
Torino created the better of the early chances, too, with Andrea Belotti firing into the side-netting and Szczesny claiming Lorenzo De Silvestri's header, but the visitors struck the first blow 33 minutes in.
They did not prove costly misses, though, as Juve saw out a ninth-straight win in the top flight ahead of a crucial run of matches, which includes league and Coppa Italia meetings with Atalanta, a trip to Lazio and the return clash with Spurs at Wembley.
Higuain appeared to twist his ankle and soldiered on for another 10 minutes before being replaced by Federico Bernadeschi, who set up the goal when he pulled the ball back for Alex Sandro to tap in just after the half hour.