Preview: Allegri will want to repeat last season's shock 2-0 victory
When both these sides met last February, not many people would have given the Rossoneri a chance at the three points. Fans filled the San Siro, hoping for a result that would send them home with a smile, and they got just that.
Goals from Kevin-Prince Boateng and Sulley Muntari sent the stadium into complete shock and excitement, even giving Mario Balotelli the chance to celebrate in the crowd amongst friends.
This time around, Barcelona is in great form, having won all their La Liga matches, with the exception of their latest against Osasuna. A scoreless draw at El Sadar eliminated Barca's chance of equaling Real Madrid's nine match win streak, but Gerardo Martino will be more focused on getting back on track Tuesday night.
Having missed a number of chances, Martino will be hoping his side can convert this time around.
"With the chances we had, we should have won," Martino told reporters. "But I'm not worried because I didn't see my team take a step back in terms of performance."
When it comes to performances, Martino cannot really complain, given his sides current run of form. They have won both their group matches in the Champions League, and they have yet to lose a match this season.
The Blaugrana traveled to Italy with a nearly full squad, with the exception of Jordi Alba, who is still out with an injury. Martino also opted to rest Messi, Pique, Dani Alves and Alexis Sanchez on Saturday, which should give the Catalans a boost.
AC Milan's domestic campaign has not been all that impressive, but they have managed to stay undefeated through two Group H matches, putting them second with four points.
"Tomorrow's match is important for everyone, but especially for the standings," Allegri told AC Milan's official website.
"It's always a fascinating game to play against them, it's a game of the highest level in Europe. They remain the strongest team in the world."
Given how poorly Milan has played thus far, Tuesday's match will not be very easy. It is likely safe to say that if Allegri was given the option of one point before kick-off, he would almost certainly take it.
Their injuries continue to pile up, and although a few players returned this past weekend against Udinese, the Rossoneri may not have enough options to cause problems for this very talented Barcelona squad.
One positive for Allegri will be the fact that Mario Balotelli may return from a slight knock, giving the Italian side a threatening option going forward. But the hosts will still be without Abbiati, De Sciglio and El Shaarawy for this match.
Where to watch the match - live stream, start time, TV channels, live scores
Watch AC Milan vs Barcelona live on Tuesday, October 22, 2013:
In Canada at 14:45 ET on: TLN en Espanol, Mediaset Italia, TVA Sports, Sportsnet Ontario / East / West / Pacific, Sportsnet World Online
In the UK at 19:45 BST on: Sky Go UK, NOT TV powered by Sky, Sky Sports 4/HD, Sky Sports Events Centre
In the USA at 14:45 ET on: Fox Sports 1, FOX Deportes, Fox Soccer 2Go, SiriusXM FC
If you are in Italy and want to follow this match live, you can do so on Premium Calcio, among others. For full TV listings in your area, be sure to check the AC Milan vs Barcelona match page.
