Franck Kessie's penalty earned Milan a 2-2 Serie A draw against Napoli, but they had to ride out a tense finale with 10 men at the San Paolo on Sunday.
Milan claimed a stunning victory over Juventus last time out and took the lead through Theo Hernandez in the first half, but goals either side of the interval from Giovanni Di Lorenzo and Dries Mertens put Napoli in control.
After Gianluigi Donnarumma let the second goal slip through his legs, Kessie spared his blushes by converting from the spot in the 73rd minute after Nikola Maksimovic felled substitute Giacomo Bonaventura.
Napoli pushed for a winner after Alexis Saelemaekers picked up two bookings in as many minutes, but Milan avoided a blow to their hopes of European qualification and the difference between the sides remains at two points.
Stefano Pioli's side owed a debt to Donnarumma for stopping them from falling behind in the early exchanges, as he thwarted Mertens before diving on Jose Callejon's scuffed effort from six yards in the 19th minute.
Milan took full advantage by going straight up the other end and taking the lead, Hernandez volleying home at the back post after Ante Rebic showed great awareness to pick him out.
However, Napoli got back on level terms when Donnarumma failed to deal with a whipped free-kick from Lorenzo Insigne and Di Lorenzo stuck the loose ball into the open goal.
Milan started the second half positively but fell behind when Callejon cut the ball back to Mertens, his low drive finding a way through Donnarumma as it squirmed over the line.
Pioli responded by sending on Bonaventura and he won the spot-kick that Kessie coolly converted into the bottom-left corner.
Substitute Saelemaekers chopped down Di Lorenzo and Eljif Elmas in quick succession to leave Milan a man light for the final three minutes of normal time, though the visitors stood firm.
What does it mean? Gattuso held by former club
Gennaro Gattuso won the Scudetto and the Champions League twice each with Milan during his playing career, but his tenure as coach was far less successful.
He already has a Coppa Italia trophy to his name during his time in the dugout at Napoli and, in his first match against his old team, he almost claimed a victory over the Rossoneri.
While he will be disappointed to have been denied all three points, he at least extended Napoli's unbeaten league run against Milan to 11 games.
Magical Mertens not enough
After being denied by Donnarumma following a lovely dribble in the first half, Mertens got the better of the goalkeeper on the hour mark. He linked the play well and also created two chances for his team-mates.
Saelemaekers sees red
Saelemaekers replaced the disappointing Lucas Paqueta at half-time but added little for Milan before leaving them under unnecessary late pressure with a pair of needless rash challenges.
Milan host Parma at San Siro on Wednesday, while Napoli are away to Bologna on the same day.