Knowing that perhaps only the winner of this match would have any remote chance of catching leaders Inter, it was a cagey start from these ‘best-of-the-rest’ sides.
The first trouble came when Vanja Milinkovic-Savic charged out and missed a Milan free-kick delivery, but the best that Strahinja Pavlovic could do was plant his header past the post.
Leonardo Spinazzola then threatened for the hosts with a trademark cut inside and right-footed curler, and Mike Maignan was rooted to the spot as it sailed a whisker away from the top corner.
That was about it for action in an uneventful first half, but the play was far more stretched after the break.
Most of the good work was done by Napoli, who saw Giovane’s rasping shot turned past the post by Maignan, while Milan hardly troubled at the other end.
The introduction of Alisson Santos also looked promising for the hosts, and his influence indirectly resulted in Frank Anguissa’s header being collected easily by the Milan goalkeeper.
But it was another Napoli substitute who ultimately made the difference. Just five minutes after coming on, Politano pounced onto Koni De Winter’s weak clearing header at the back post and rasped a powerful volley low into the net.
Only then did Milan’s attack ignite, though efforts from their own replacements, Santiago Gimenez and Rafael Leao, weren’t enough to prevent a fruitless trip to Campania.
The result means Napoli jump to within seven points of Inter, though they won’t get the opportunity to take any points off the Nerazzurri in the final seven matchdays.
They leapfrog Milan, who lose for just a second time on the road this season and miss the chance to complete a league double over Napoli for the first time since 2010/11.