A big bugbear of Celtic fans is Lennon’s preference for 3-5-2 despite the issues it has presented. Nir Bitton, Hatem Abd Elhamed and Christopher Jullien remain out. Does the Parkhead boss stick with the system which was used in the listless loss to Rangers at the weekend?
Stephen Welsh was brought in for just his second ever start in the league.
The sensible move could be reverting to a back four. With AC Milan also playing a lone striker, three at the back, plus Scott Brown in front could be deemed as overkill.
Duffy v Ibrahimovic
The Republic of Ireland international centre-back has come in for criticism for his performances since arriving at Parkhead in the summer, something which intensified following the loss to Rangers.
The loan signing from Brighton has looked susceptible to simple balls over the top, while his use of the ball on Saturday was, at best, erratic.
Up against Zlatan Ibrahimovic could suit Duffy. The Swede is unlikely to run in behind and will look for the ball into his feet. Instead, he will likely drop to allow runners in behind. Lennon could be tempted to instruct his centre-back to stay tight, narrow the full-backs and simply allow Duffy to confront and man mark Zlatan.
There is every chance Celtic could be forced into plenty of defending around the penalty box, something which Duffy has excelled at through his career.
Who plays left?
The decision as to who plays on the left side of defence or as wing-back could be determined by the formation.
Greg Taylor is much more comfortable as an orthodox full-back, keen to defend and capable of support, whereas Diego Laxalt is more suited to the wing-back role and would provide more attacking thrust.
However, Laxalt’s familiarity with AC Milan, having been signed on loan from the Italian giants could be a key factor in Lennon’s decision, even if he reverts to a back four.
As well as Lennon's use of the 3-5-2, he has also come in for criticism for his loyalty to captain Scott Brown. The midfielder has largely been underwhelming this season, sitting as a base in front of a back three.
In the same role against AC Milan could prove very difficult for the player and in turn the team. It would mean a lot of space for Brown to cover, leaving him overworked against a team with plenty of intelligent movement.
Brown could be helped – whether in a 3-5-2 or 4-2-3-1 – by Callum McGregor slotting alongside him at the base of the midfield and doing a similar job to the one he has done recently for Scotland where there has been more onus on the defensive side of his game.
Odsonne Edouard is out. The latest blow for Lennon. However, Ryan Christie is available again and opens options in attack. He could play on the right of a 4-2-3-1, through the centre as a No.10 or as a second striker in the 3-5-2.
As for the striker, Patryk Klimala struggled against Rangers. It could mean a start of Albian Ajeti.