Gonzalo Higuain scored the winner against his former club as Juventus extended their Serie A lead with victory at home to third-placed Napoli.
Higuain left Napoli in an acrimonious Italian-record £75m move this summer and did not celebrate after smashing home a loose ball with 20 minutes left.
Jose Callejon had drawn Napoli level with a deft finish after Leonardo Bonucci gave Juve the lead.
The win moves Juve five points clear of Roma, who play at Empoli on Sunday.
Higuain scored a record 36 Serie A goals for Napoli last season, and many of the club’s supporters were not happy about his decision to leave.
After the move, fans publicly threw their Higuain shirts, banners and scarves into dustbins, while before Saturday’s match Napoli manager Maurizio Sarri said of the Argentina striker: “I’ll greet him like a father does with a son who made him angry.”
Higuain was spared having to play in front of any travelling fans as they were banned from attending for security reasons.
However, he still sent a message with the manner of his celebration – by extending his arms out wide and opening his hands in a gesture of apology.
The 28-year-old might have added a second but badly miscued a header, leaving Napoli with hope of grabbing an equaliser late on.
But Dries Mertens spurned their best chance in injury time when he fired over from close range.
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