Milan returned to the Serie A summit with a 2-0 win at Benevento as Stefano Pioli's side survived playing with 10 men for almost an hour.
With rivals Inter having gone top after a 6-2 thrashing of Crotone earlier on Sunday, the Rossoneri responded with a gritty victory at Stadio Ciro Vigorito.
Franck Kessie scored a first-half penalty but Sandro Tonali was dismissed before the interval to make it a potentially uncomfortable evening for the visitors.
However, Pioli's men dug deep and Rafael Leao produced a moment of magic four minutes into the second half, with Gianluca Caprari's missed spot-kick robbing Benevento of a golden chance to get back into the match.
With champions Juventus up next, Milan have a chance to send out a signal to the rest of the division that this really could be their year.
Brahim Diaz flashed an early long-range shot over the crossbar as the visitors, unbeaten in 14 on the road, signalled their intent.
Benevento were the architects of their own downfall as Milan took the lead after 15 minutes, a defensive mix-up ending with Alessandro Tuia felling Ante Rebic in the box, with Kessie coolly converting the subsequent spot-kick.
Roberto Insigne came within inches of pulling the hosts level but saw his fine strike crack the inside of Gianluigi Donnarumma's left-hand upright.
Filippo Inzaghi, who played at San Siro for over 10 years, saw his Benevento side handed a boost when Tonali was shown a red card for a careless lunge on Artur Ionita.
The home side tried to force the issue as Gianluca Caprari and Gaetano Letizia both fired off dangerous efforts, but Milan made it to the break with their lead intact.
Pioli's charges earned the breathing space they so desperately craved courtesy of a fine goal from Leao, who beat Lorenzo Montipo to Rebic's throughball and turned smartly before lifting a pinpoint finish over the stranded goalkeeper.
Benevento's frustrations deepened when Caprari dragged a woeful penalty wide after Rade Krunic had clumsily fouled him in the area, with Milan almost adding a late third when Kessie's low shot hit the inside of the post and rolled across the line.