To the surprise of many pundits and fans, the Hoops emerged ahead of Benfica and Spartak Moscow to finish second in Group G behind star-studded Barcelona - whom they famously beat 2-1 at Celtic Park last November - and earn their place in the knockout stages of the tournament for the first time in five seasons.
The Serie A champions, though, are strong favourites to progress through to the quarter-finals but manager Lennon, while recognising the quality of the visitors, said: "I think we have been (underestimated) throughout the whole campaign and going into this game we are being made out to be massive underdogs but I don't quite see it that way myself."
He added: "There is a real belief, anything can happen over two games.
"We go into the tie as underdogs but nothing is going to be decided at the end of 90 minutes tomorrow night, it is over two games and we are prepared to play hard football over 180 minutes.
"They have excellent strikers - Mirko Vucinic, Fabio Quagliarella, Sebastian Giovinco, and they have also brought in Nicolas Anelka, but the one who has caught my eye is Alessandro Matri, he looks an excellent young player.
"They are very strong in midfield. Arturo Vidal is playing very well currently, Paul Pogba and Claudio Marchisio, these are class players including Andrea Pirlo who is still one of the finest midfield players in the world.
"So the team is blessed with fantastic footballers but we knew that before the tie or before any preparation were made.
"But it would be dangerous to underestimate Celtic.
"We have proved already this season that we can be a match for anyone."
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