The Portuguese winger helped the Serie A side win their first Scudetto in a decade last season, finishing the campaign with 11 goals and 10 assists, and was the recipient of the Serie A MVP award.
And, despite a red card against Sampdoria, he has begun the new season equally well, and has already found the net four times in this campaign.
That form was enough to excite the attention of Chelsea in the summer, but, at the time, they pulled back from making a formal offer for him, judging his £110 million release clause prohibitive.
However, the Premier League side have retained their interest and may be tempted to return for him in January.
They may now face competition from a familiar source, though, with Manchester United also tracking developments.
Erik ten Hag is reported to be a big admirer of the 23-year-old, and had him watched by scouts during Milan’s two matches with Chelsea in the Champions League.
It has also been suggested that Manchester City are keeping tabs on developments as well.
Leão was signed from the French side Lille for £27 million in the summer of 2019, and is under contract at the San Siro until 2024.
The Serie A side are desperate to keep him, and have opened talks with him about a new deal, but may baulk at his contract demands, with him reported to be wanting £120,000 a week. He also wants the club to pay a contribution to the £14 million he was ordered to pay to former club Sporting Lisbon by a court.
At the Ballon D’Or ceremony AC Milan director Daniele Massaro indicated they would be meeting the star’s father and agent, to discuss a new contract, but, at the same time, Leão will know he holds the balance of power, especially if he has a good World Cup with Portugal, which will only increase his market value further.
If AC Milan want to retain him, they should try and get him tied down as a matter of priority, otherwise the economics will start to work against them.
At the end of the season he will be entering the final year of his deal and that will be their last chance to earn some serious money for him.
He may well end up staying in Italy, but that will still be an expensive option for the Milanese.