Milan and Napoli enjoyed parallel unbeaten runs in their opening 12 league games of the season.
Having been top of the standings previously, Napoli knew a fourth defeat in six league games would seriously hurt.
Now, after the 1-0 home victory for the Napolitanas, Napoli and AC Milan are both on 39 points.
Both teams were missing several key players through injury and it played out in an ugly affair low on quality.
Serie A Football Results – Napoli Beat AC Milan 1-0 at the San Siro
Midfielder Eljif Elmas glanced a header home at the near post from a corner to stun the hosts.
So, Napoli edged out the visitors in the fifth minute, and held this 1-0 lead easily until the latter stages. Napoli thus gave themselves the perfect platform with Elmas’ early opener.
Veteran Milan striker Zlatan Ibrahimovic looked most likely to find an equaliser for the visitors. He came close to scoring twice, midway through the first half and then just after the break.
In the 90th minute, as Milan looked out of ideas, Franck Kessie seemingly snatched a point, sparking wild celebrations.
However, VAR ruled this goal out for offside against Olivier Giroud as he lay on the ground in the penalty area.
Milan were furious with the call which allowed Napoli their first win in four league games and reach 39 points. This is the same as Milan, but they’re now above Stefano Pioli’s team on goal difference.
All the drama took place right at the death. Kessie’s effort was scrappy but Milan did not care one bit as even Stefano Pioli ran to join the celebrations.
But VAR asked referee Davide Massa to have another look at the goal on the pitch side monitor. Consequently, Massa ruled that substitute Giroud, prone on the turf, was offside when attempting to get involved in the build-up.