Leao played a vital part in helping AC Milan claim the Serie A title last season, making 34 appearances and notching eleven goals along with ten assists.
His impressive form saw him become of interest to Chelsea in the summer and they lodged a bid with AC Milan last month.
The bid was rejected and Leao continued with AC Milan but Chelsea are looking at snatching him away from the Italian giants in January.
Chelsea are continuing to keep tabs on the winger as he is one of the foremost names on the club’s wish list for January, according to Italian daily Gazzetta dello Sport.
The Blues’ resolve to get hold of the Portuguese star could be further strengthened should he have a good World Cup near the end of the year.
AC Milan however are not in the mood to roll over for Chelsea, and are working on getting the attacker to extend his contract with them.
Leao has started off the current season in the same vein as the previous, playing eight matches so far and registering three goals along with six assists.