Fikayo Tomori cost Milan around £25million when he joined from Chelsea, and on Wednesday he will return to face the Premier League giants.
Milan head to Stamford Bridge for the first time since 1999, while Paris Saint-Germain's Kylian Mbappe is out to make club history.
Celtic are in need of a positive result as they make the trip to face RB Leipzig in the Champions League tonight. After an opening defeat to Real Madrid in Glasgow, Ange Postecoglou’s side were impressive for large periods against Shakhtar Donetsk but could not turn that into three points as they were held to a 1-1 draw last time out. It leaves them third in Group F, ahead of two matches in a week against Leipzig who sit bottom of the group after defeats to both Real and Shakhtar, conceding six goals in the process.
Ex-Liverpool boss Rafael Benitez and former Burnley manager Sean Dyche are seen as possible replacements.