The supporter wanted a selfie with the Portugal winger, who was already a favourite after the way he played in Milan's Serie A title triumph but is now being spoken of in the sort of tones as for the past icons who made them seven-time European champions.
After hitting double figures for both goals and assists last season the 23-year-old had started this campaign in even more spectacular form, scoring four times and setting up six more in all competitions.
Milan's only defeat of the season came in the one match Leao has missed, against Serie A leaders Napoli.
And although Stefano Pioli's team have been hit with a raft of injuries -- France's Theo Hernandez and Mike Maignan among those on the treatment table -- Leao's form has them travelling to London in high spirits.
Saturday's incredible win was a perfect example of both Milan's never-say-die spirit and mercurial talent of their star man, who had a hand in all three of the Rossoneri's goals.
Having set up Ante Rebic's 79th-minute opener with a typically devastating display of dribbling, Leao also launched the pass which eventually led to Fode Ballo-Toure putting Milan back in front in stoppage time.
He then capped off a dramatic win in the most stylish of fashions with 96 minutes on the clock, racing towards goal before scooping a perfect finish over Guglielmo Vicario.
- 'No one is unsellable' -
Red-hot Leao will be the key man at Stamford Bridge as Milan attempt to hold top spot in Champions League Group E, which they lead by one point from Dinamo Zagreb, and increase their hopes of making the knockout stages for the first time since the 2013-14 season.
A good performance will surely increase the Blues' interest in Leao after they made an informal bid to Milan in the close season.
Milan value Leao at well over 100 million euros ($98 million) and want to get maximum value from an asset they know will eventually join one of football's financial heavyweights, a status they once held in Silvio Berlusconi's heyday.
Club legend and technical director Paolo Maldini confirmed last month that Milan had rejected an offer from Chelsea but added that "it's pointless being a romantic... When offers of a certain type are made, no one is unsellable."
Milan are trying to get Leao to extend his current deal which runs to 2024, and Italian daily Corriere Della Sera report that they are offering 6-7 million euros a year in a bid to stave off interest from the Premier League.
They are hoping to get the new deal signed before the World Cup, when Leao will have the chance to shine on the biggest stage of all.
Portuguese outlet Record also claim that Maldini has met with Sporting Lisbon director Frederico Varandas twice as part of discussions over the 20 million euros Leao has to pay his former club.
Leao unilaterally terminated his contract with Sporting in 2018 after fans invaded the club's training ground, joining Ligue 1 side Lille.
And Milan are reportedly trying to cut a deal with the Portuguese club in the hope it will convince Leao to stay long-term at the San Siro -- which fans are packing out thanks in part to Leao's development into one of the world's best.
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