Milan will be Milan, whoever is wearing the famous red and black strips, and they have enough quality in depth to be a real force.
What really matters is how the players selected by Neil Lennon perform in this opening match of Group H.
They have already proved they can compete with the very best, as they did against Barcelona in two ties last season.
They have shown they can defy the odds, handle the pressure - and deliver when it counts.
Think of Moscow, and the wonderful nights at Celtic Park. How good they felt. These are the thoughts they have to take with them into the San Siro this evening.
Any sign of an inferiority complex will be seized upon by the Milan players, even if their own team is not a recognisable XI.
Perhaps Neil would have preferred more of the established names to be in there as that way he would have had a better idea of how they will set up and the system they will adopt.
He does his homework very well, and that included flying in to watch Milan play Torino on Saturday to update himself on how they are performing.
But, as I said, it is how Celtic play that matters more than anything, and that is something over which Neil does have control.
I expect to see him set up with a lone striker, and I think Anthony Stokes will get his long-awaited chance to show he can fill that role at this level.
He prefers to have a partner alongside, but I can't see Neil changing his system to accommodate this, so Anthony will have to settle for having Kris Commons supporting him from behind.
That will allow Georgios Samaras to go into a wide left position, where he is most effective in an attacking sense.
With James Forrest unavailable, Neil can get pace on the other side through Derk Boerrigter, who looked good against Hearts at the weekend.
If Joe Ledley doesn't recover from his groin injury, Charlie Mulgrew can partner Scott Brown as the two holding midfielders.
But if Joe makes it, I'd play Charlie at left-back rather than Emilio Izaguirre as his height will be a big advantage.
Similarly, Mikael Lustig can be a big barrier to any Milan attack down their left, and offer cover for Efe Ambrose and Virgil van Dijk as they try to keep Mario Balotelli quiet.
The big enigma can be a real handful, depending on what mood he is in.
But whoever is detailed to pick up Balotelli, my instructions to them would simply be: "Deal with him. Whatever it takes, deal with him."
It's going to be a real test for Virgil, playing his first group game for the club.
But Efe is also under pressure to perform after a few iffy games when his concentration has wavered at key moments.
He showed in the Nou Camp that, when he fully switched on, he can deal with the very best strikers.
But, Neil has to remind him that, if you switch off for a second at this level, you will be punished.
Milan will be right up for it. They will expect Barcelona to win against Celtic when they go to Spain, and will feel they must get maximum points against them tonight.
It is going to be a tight battle for those qualification places, and no one will want to lose ground at the start.
Yes, there are five games after tonight in which to catch up. But you really don't need to put yourself under extra pressure - especially with Barca at Celtic Park next.
The tactics Neil has tended to adopt in games like this have been to keep it tight, hit on the break, and score first to give something to hold on to.
However, you have to be sure not to hand the opposition the initiative, and most important of all is you must not make any unforced errors.
The San Siro does not hold happy memories for me as it's where we lost the 1970 European Cup final.
But it is a fantastic stadium in which to play football. Then again, so is Celtic Park, so no one should freeze on the night.