Milan, who lifted the European Cup for the seventh time by defeating Liverpool 2-1 in Athens nearly five years ago, have since been eliminated from the Champions League by Arsenal, Manchester United and Tottenham Hotspur and could only draw with Portsmouth in the group stage of the Europa League in 2009.
They now face Arsene Wenger's erratic team again, the Londoners having knocked Milan out in the last 16 in 2008.
Serie A leaders Milan welcome striker Zlatan Ibrahimovic back from a domestic ban to boost their chances after they ended a bad patch with Saturday's late 2-1 win at Italian title rivals Udinese where young forward Stephan El Shaarawy and new signing Maxi Lopez combined for the goals.
"It meant a lot to win at Udine, we'd just come off three defeats in five games," coach Allegri told reporters.
"That win has given us balance and serenity. This is the sprit of the guys, we have to move forward like this."
The key to Wednesday's game is what tactics Wenger employs and whether he plays safe for a draw or attempts to go for a third straight win against Milan in their own backyard.
Wenger could be wary of Milan's attacking prowess and play it cautiously but their Welsh midfielder Aaron Ramsey believes away goals could prove critical in this tie.
He told Arsenal TV Online: "If we can go there and get a few goals and then come back to the Emirates then that's going to be a fantastic result for us.
"Hopefully, we can get a couple of goals and keep them out as well."
Arsenal's fortunes have revived since French striker Thierry Henry rejoined the club on loan from New York Red Bulls, and if he does play any part on Wednesday, it is likely to be his final appeareance in an Arsenal shirt.
