Daniel Maldini was on target in his first Serie A start as Milan relied on Brahim Diaz's late winner to edge past Spezia 2-1 on Saturday.
Maldini, son of Italy and Rossoneri legend Paolo, enjoyed a dream maiden top-flight start as he headed Stefano Pioli's side into the lead after the interval at the Alberto Picco Stadium.
However, Daniele Verde's deflected effort levelled things up with just over 10 minutes to go before Diaz restored the visitors' lead in the closing stages.
Milan banished their demons from the shock 2-0 defeat in this fixture last term to move a point clear at the summit, though the chasing pack do have a game in hand.
M'Bala Nzola tested Mike Maignan twice early on, first from range and then from distance, but the Milan goalkeeper parried both away before Theo Hernandez whipped a free-kick narrowly wide.
Ante Rebic should have opened the scoring from Sandro Tonali's corner but his free header was wayward as Milan failed to make their 62 per cent first-half possession pay.
However, Maldini – appearing 12 years and 117 days after his father Paolo's last league appearance – powered a header home three minutes after the break from Pierre Kalulu's delivery to open the scoring.
Rafael Leao – one of Piolo's two-half time changes – looked to have added a second but he was denied by the right-hand post before Giulio Maggiore turned over from point-blank range following Simone Bastoni's teasing cross.
Leao again went close moments later as he dragged an effort wide to the right and Milan's failure to kill the game off came back to haunt them.
Verde twisted and turned before firing a low left-footed strike, which hit Tonali and left Maignan powerless to stop Spezia from drawing level in the closing stages.
Diaz proved the late hero as he ghosted into the area to turn home Alexis Saelemaker's low delivery and secure the win for Milan.