Rafael Leao ended a difficult week with the only goal in Saturday's 1-0 win over Verona which drew AC Milan level with Serie A leaders Inter Milan, while Juventus fell to their first defeat of the season, 4-2 at Sassuolo.
Portugal winger Leao netted his third goal in as many league matches in the eighth minute at a sodden San Siro to move Milan up to second on 12 points from five games.
Inter defend their 100 per cent start at rock-bottom Empoli on Sunday.
Leao's winner was one of the few highlights of a largely uninspiring performance from a much-changed Milan side missing injured captain Davide Calabria and France pair Mike Maignan and Theo Hernandez.
But it was a welcome three points after being destroyed by local rivals Inter last weekend and failing to capitalise on their dominance in Tuesday's Champions League stalemate with Newcastle United.
Milan's star man Leao, wearing the skipper's armband in Calabria's absence, answered some of his critics following poor displays in both of those matches, even becoming a figure of fun for falling over his own feet while trying to backheel in a goal against Newcastle.
"Rafa did what he needed to do," said Milan coach Stefano Pioli.
"He just needs to keep going and realise that when you become a great player you need to overcome or at least deal with a lot of pressure."
Kick-off was delayed by nearly half an hour due to a sudden hailstorm which battered Milan, and the away fans then ruined the pre-match minute's silence in honour of former Italian president Giorgio Napolitano, who died aged 98 on Friday.
Napolitano, who was head of state between 2006 and 2015, was a leading member of Italy's Communist Party from the 1970s until its most right-wing in a country where fascist fan
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